JP2018191330A - Power control and power headroom reporting in dual connectivity - Google Patents

Abstract

A method for efficiently executing power control in a situation where a mobile station is connected to both a master base station and a secondary base station. A mobile station is connectable to a master base station via a first radio link, and is connectable to at least one secondary base station via a second radio link. The mobile station calculates a first power headroom report of the first radio link with the master base station, and calculates the calculated first power headroom report to the second base station with the secondary base station. Information on the radio link path loss is transmitted to the master base station along with information that allows the master base station to determine. The mobile station calculates a second power headroom report of the second radio link with the secondary base station, and transmits the calculated second power headroom report to the secondary base station. [Selection] Figure 21

Description

  The present disclosure provides an integrated circuit that performs improved power headroom reporting and power distribution control.

Long Term Evolution (LTE)
Third generation mobile communication systems (3G) based on WCDMA® radio access technology are being deployed on a wide scale around the world. HSDPA (High-Speed Downlink Packet Access) and Enhanced Uplink (also referred to as HSUPA (High Speed Uplink Packet Access)) were introduced as the first steps in enhancing, developing and evolving this technology. Provides a highly competitive wireless access technology.

  3GPP has introduced a new mobile communication system called LTE (Long Term Evolution) in order to meet the increasing demand from users and ensure competitiveness for new radio access technologies. LTE is designed to provide the carrier required for high speed data and media transmission and high volume voice support over the next decade. The ability to provide high bit rates is an important strategy in LTE.

  The specifications of work items (WI) related to LTE (Long Term Evolution) are called E-UTRA (Evolved UMTS Terrestrial Radio Access (UTRA)) and E-UTRAN (Evolved UMTS Terrestrial Radio Access Network (UTRAN)). Will be released as Release 8 (LTE Release 8). The LTE system is a packet-based efficient radio access and radio access network that provides all IP-based functions with low latency and low cost. In LTE, to achieve a flexible system deployment using a given spectrum, multiple scalable transmission bandwidths (eg, 1.4 MHz, 3.0 MHz, 5.0 MHz, 10.0 MHz, 15.0 MHz, And 20.0 MHz) are specified. The downlink employs radio access based on OFDM (Orthogonal Frequency Division Multiplexing). This is because such wireless access is inherently less susceptible to multipath interference (MPI) due to its low symbol rate, uses cyclic prefix (CP), and has various transmission bandwidths. It is because it can respond to the configuration. The uplink employs radio access based on SC-FDMA (Single-Carrier Frequency Division Multiple Access). This is because, given the limited transmission output of the user equipment (UE), priority is given to providing a wider coverage area than to improve the peak data rate. In LTE Release 8/9, a number of major packet radio access technologies (for example, Multiple-Input Multiple-Output (MIMO) channel transmission technology) are employed to achieve a highly efficient control signaling structure.

LTE Architecture FIG. 1 shows the overall architecture of LTE, and FIG. 2 shows the E-UTRAN architecture in more detail. E-UTRAN is composed of eNodeB, which terminates E-UTRA user plane (PDCP / RLC / MAC / PHY) and control plane (RRC) protocols for UE. The eNodeB (eNB) includes a physical (PHY) layer, a media access control (MAC) layer, a radio link control (RLC) layer, and a packet data control protocol (PDCP) layer. (These layers include user plane header compression and encryption functions). The eNB also provides a radio resource control (RRC) function corresponding to the control plane. eNB performs radio resource management, admission control, scheduling, negotiated uplink QoS (Quality of Service), cell information broadcast, user plane data and control plane data encryption / decryption, downlink / uplink users Performs many functions, such as plain packet header compression / decompression. The plurality of eNodeBs are connected to each other by an X2 interface.

  In addition, a plurality of eNodeBs are configured by an EPC (Evolved Packet Core) through an S1 interface, more specifically, an MME (Mobility Management Entity) through S1-MME, and a serving gateway (SGW: Serving Gateway) through S1-U. It is connected to the. The S1 interface supports a many-to-many relationship between the MME / serving gateway and the eNodeB. While the SGW routes and forwards user data packets, it functions as a mobility anchor for the user plane during handover between eNodeBs, and also an anchor for mobility between LTE and another 3GPP technology (S4 Terminates the interface and relays traffic between the 2G / 3G system and the PDN GW). The SGW terminates the downlink data path for idle UEs and triggers paging when downlink data arrives for that UE. The SGW manages and stores UE context (eg, IP bearer service parameters, network internal routing information). In addition, the SGW performs replication of user traffic in case of lawful interception.

  The MME is the main control node of the LTE access network. The MME is responsible for idle mode UE tracking and paging procedures (including retransmissions). The MME is involved in bearer activation / deactivation process, and also the role of selecting the UE's SGW during initial attach and during intra-LTE handover with relocation of core network (CN) nodes Also bears. The MME is responsible for authenticating the user (by interacting with the HSS). Non-Access Stratum (NAS) signaling is terminated at the MME, which is also responsible for generating a temporary ID and assigning it to the UE. The MME checks the UE's authentication to enter the service provider's Public Land Mobile Network (PLMN) and enforces the roaming constraints of the UE. The MME is a termination point in the network in encryption / integrity protection of NAS signaling, and manages security keys. Lawful interception of signaling is also supported by the MME. In addition, the MME provides a control plane function for mobility between the LTE access network and the 2G / 3G access network and terminates the S3 interface from the SGSN. Furthermore, the MME terminates the S6a interface towards the home HSS for the roaming UE.

Component Carrier Structure in LTE A downlink component carrier (CC) in 3GPP LTE system is divided into so-called subframes in the time-frequency domain. In 3GPP LTE, as shown in FIG. 3, each subframe is divided into two downlink slots, and the first downlink slot is a control channel region (PDCCH region) in the first few OFDM symbols. including. Each subframe consists of a specific number of OFDM symbols in the time domain (12 or 14 OFDM symbols in 3GPP LTE (Release 8)), each of which covers the entire bandwidth of the component carrier. Therefore, each OFDM symbol is composed of a plurality of modulation symbols transmitted on N ^DL _RB * N ^RB _sc subcarriers as shown in FIG.

For example, when considering a multi-carrier communication system that employs, for example, OFDM used in 3GPP LTE (Long Term Evolution), the minimum unit of resources that can be allocated by the scheduler is one “resource block”. As illustrated in FIG. 4, the physical resource block (PRB) includes N ^DL _symb continuous OFDM symbols (eg, 7 OFDM symbols) in the time domain and N ^RB _{sc sc} in the frequency domain. Defined as consecutive subcarriers (eg, 12 subcarriers of component carriers) Therefore, in 3GPP LTE (Release 8), a physical resource block consists of N ^DL _symb * N ^RB _sc resource elements, corresponding to 1 slot in the time domain and 180 kHz in the frequency domain (for the downlink resource grid). For further details, see, for example, Section 6.2 of Non-Patent Document 1) (available on the 3GPP website and incorporated herein by reference).

A subframe consists of two slots, so there are 14 OFDM symbols in a subframe when a so-called “normal” CP (cyclic prefix) is used, so-called “extended” CP is used. When there are 12 OFDM symbols in a subframe. As a terminology, in the following, a time-frequency resource equal to the same N ^RB _sc consecutive subcarriers throughout a subframe is referred to as a “resource block pair” or, in the same sense, an “RB pair” or “PRB pair”. Called.

  The term “component carrier” means a combination of several resource blocks in the frequency domain. In future releases of LTE, the term “component carrier” will no longer be used. Instead, the term is changed to “cell”, which means a combination of downlink resources and optionally uplink resources. The linking between the carrier frequency of the downlink resource and the carrier frequency of the uplink resource is indicated in the system information transmitted on the downlink resource. Similar assumptions for the component carrier structure apply to subsequent releases.

Carrier aggregation in LTE-A to support wider bandwidth
In World Radio communication Conference 2007 (WRC-07), the frequency spectrum of IMT-Advanced was determined. Although the overall frequency spectrum for IMT-Advanced has been determined, the actual available frequency bandwidth varies by region or country. However, following the determination of the outline of the available frequency spectrum, standardization of the radio interface has been started in the 3rd Generation Partnership Project (3GPP). At the 3GPP TSG RAN # 39 meeting, the description of the Study Item on “Further Advancements for E-UTRA (LTE-Advanced)” was approved. This Study Item covers technical elements that should be considered in order to evolve and develop E-UTRA (for example, to meet the requirements of IMT-Advanced).

  The bandwidth that the LTE-Advanced system can support is 100 MHz, but the LTE system can only support 20 MHz. Recently, the lack of radio spectrum has hindered the development of radio networks, and as a result, it is difficult to ensure a sufficiently wide spectrum band for LTE-Advanced systems. Therefore, finding a way to obtain a wider radio spectrum band is an urgent task and one possible answer is the carrier aggregation function.

  In carrier aggregation, two or more component carriers (cells) are aggregated (combined) for the purpose of supporting a wide transmission bandwidth of up to 100 MHz. In LTE-Advanced systems, some cells in the LTE system are aggregated into a wider channel, which is sufficient for 100 MHz even if these cells in LTE are in different frequency bands. wide.

  When the number of aggregated component carriers is at least the same in the uplink and downlink, all component carriers can be configured as LTE Release 8/9 compatible. All component carriers aggregated by the UE may not necessarily be LTE Release 8/9 compatible. To avoid release 8/9 UEs camping on component carriers, existing mechanisms (eg, burring) can be used.

  The UE can simultaneously receive or transmit one or more component carriers (corresponding to multiple serving cells) depending on its capabilities. An LTE-A Release 10 UE with reception capability and / or transmission capability for carrier aggregation can receive and / or transmit simultaneously on multiple serving cells. In contrast, LTE Release 8/9 UEs can receive and transmit on only one serving cell if the component carrier structure follows the Release 8/9 specification.

  Carrier aggregation is supported on both contiguous and discontinuous component carriers, where each component carrier has a maximum of 110 in the frequency domain when using 3GPP LTE (Release 8/9) calculation scheme. Limited to resource blocks.

  3GPP LTE-A (Release 10) compatible UEs to aggregate different numbers of component carriers transmitted from the same eNodeB (base station) (possibly different bandwidths in uplink and downlink) It is possible to set. The number of downlink component carriers that can be configured depends on the UE's downlink aggregation capability. Conversely, the number of uplink component carriers that can be configured depends on the UE's uplink aggregation capability. The mobile terminal cannot be configured such that there are more uplink component carriers than downlink component carriers.

  In a typical TDD deployment, the number of component carriers and the bandwidth of each component carrier are the same on the uplink and downlink. Component carriers transmitted from the same eNodeB need not necessarily provide the same coverage.

  The interval between the center frequencies of the component carriers that are continuously aggregated is a multiple of 300 kHz. This is to maintain compatibility with the 100 kHz frequency raster of 3GPP LTE (Release 8/9) while maintaining the subcarrier orthogonality at 15 kHz intervals. In some aggregation scenarios, n * 300 kHz spacing can be facilitated by inserting a few unused subcarriers between consecutive component carriers.

  The impact of aggregating multiple carriers only extends to the MAC layer. The MAC layer requires one HARQ entity for each aggregated component carrier in both uplink and downlink. There is a maximum of one transport block per component carrier (when not using SU-MIMO in the uplink). The transport block and its HARQ retransmission (when it occurs) need to be mapped to the same component carrier.

  FIG. 5 and FIG. 6 illustrate the layer 2 structure with carrier aggregation enabled in the downlink and uplink, respectively.

When carrier aggregation is set, the mobile terminal has only one RRC connection with the network. Upon establishment / re-establishment of RRC connection, one cell, like LTE Release 8/9, has security inputs (one ECGI, one PCI, and one ARFCN) and non-access layer (NAS) mobility information ( Example: TAI). After establishment / re-establishment of the RRC connection, the component carrier corresponding to that cell is referred to as the downlink primary cell (PCell). In the connected state, one downlink PCell (DL PCell) and one uplink PCell (UL PCell) are always set per UE. A cell other than the primary cell in the set of configured component carriers is referred to as a secondary cell (SCell), and the carrier of the SCell includes a downlink secondary component carrier (DL SCC) and an uplink secondary component carrier (UL SCC). It is. The characteristics of the downlink PCell and the uplink PCell are as follows.
-For each SCell, the use of uplink resources in addition to downlink resources by the UE can be configured. Therefore, the number of DL SCCs configured is always greater than or equal to the number of UL SCCs, and the SCell cannot be configured to use only uplink resources.
-Uplink PCell is used to transmit layer 1 uplink control information.
-Downlink PCell cannot be deactivated unlike SCell.
-From the UE perspective, each uplink resource belongs to only one serving cell.
-The number of serving cells that can be configured depends on the aggregation capabilities of the UE.
-Re-establishment is triggered when Rayleigh Fading (RLF) occurs in the downlink PCell, but re-establishment is not triggered even if RLF occurs in the downlink SCell.
-Downlink PCell may be changed by handover (ie security key change and RACH procedure).
-Non-access layer information is obtained from the downlink PCell.
-The PCell can only be changed by a handover procedure (ie security key change and RACH procedure).
-PCell is used for transmission of PUCCH.

  Configuration and reconfiguration of the component carrier can be performed by RRC. Activation and deactivation are performed via a MAC control element (MAC CE). Furthermore, at the time of handover within LTE, the SCell for use in the target cell can be added, deleted, or reconfigured by RRC. When adding a new SCell, dedicated RRC signaling is used to send SCell system information (necessary for transmission / reception) (similar to handover in LTE Release 8/9).

  When the UE is configured to use carrier aggregation, a pair of uplink component carrier and downlink component carrier is always active. The downlink component carrier of this pair may be referred to as a “downlink anchor carrier”. The same is true for the uplink.

  When carrier aggregation is set, UEs can be scheduled for a plurality of component carriers at the same time, but at most one random access procedure can be performed at a time. In cross-carrier scheduling, resources of another component carrier can be scheduled by PDCCH of a certain component carrier. For this purpose, a component carrier identification field (referred to as “CIF: Component carrier Identification Field”) is introduced in each DCI format.

  When cross-carrier scheduling is not performed, the uplink component carrier to which the grant is applied can be identified by linking the uplink component carrier and the downlink component carrier. The link of the downlink component carrier to the uplink component carrier is not necessarily one-to-one. In other words, multiple downlink component carriers can be linked to the same uplink component carrier. On the other hand, one downlink component carrier can be linked to only one uplink component carrier.

In uplink access scheme uplink transmission in LTE, in order to maximize coverage, transmission with high power efficiency by the user terminal is required. As an uplink transmission scheme of E-UTRA, a scheme combining single carrier transmission and FDMA with dynamic bandwidth allocation is selected. The main reason for choosing single carrier transmission is lower peak-to-average power ratio (PAPR) compared to multi-carrier signal (OFDMA), correspondingly improving the efficiency of the power amplifier and improving coverage. This is because the data rate is high for a given terminal peak power. The NodeB assigns a unique time / frequency resource for transmitting user data to the user at each time interval, thereby ensuring orthogonality within the cell. Spectral efficiency is increased by eliminating intra-cell interference with orthogonal access in the uplink. Interference due to multipath propagation is dealt with in the base station (NodeB) by inserting a cyclic prefix into the transmission signal.

The basic physical resource used for data transmission consists of a frequency resource of size BW _grant over one time interval (eg 0.5 ms subframe) (the encoded information bits are mapped to this resource) ) A subframe (also referred to as a transmission time interval (TTI)) is a minimum time interval for transmitting user data. However, by concatenating the subframes, it is also possible to allocate the frequency resource BW _grant over a time longer than 1 TTI to the user.

Uplink Scheduling Scheme in LTE Both the scheduling controlled access (ie, controlled by eNB) and the contention based access can be used as the uplink scheme.

  For scheduling controlled access, a specific frequency resource of a specific time length (ie, time / frequency resource) is allocated to the UE for uplink data transmission. However, some time / frequency resources can be allocated for contention-based access. Within contention-based time / frequency resources, the UE can transmit without first being scheduled. One scenario where the UE performs contention-based access is, for example, random access, i.e. when the UE makes an initial access to a cell or when making an initial access to request uplink resources. .

For scheduling controlled access, the Node B scheduler allocates specific frequency / time resources for uplink data transmission to users. More specifically, the scheduler determines:
-UE (s) that allow transmission
– Physical channel resources (frequency)
-The transport format (modulation and coding scheme (MCS)) that the mobile terminal should use for transmission

  The allocation information is signaled to the UE via a scheduling grant sent on the L1 / L2 control channel. Hereinafter, this channel is referred to as an uplink grant channel for the sake of brevity. The scheduling grant message includes at least a portion of the frequency band that is allowed to be used by the UE, a validity period of the grant, and a transport format that the UE must use for uplink transmission to be performed in the future. . The shortest valid period is one subframe. The grant message can also include additional information depending on the scheme selected. Only grants “for each UE” are used as grants that grant the right to transmit on the uplink shared channel (UL-SCH) (ie, there is no grant “for each radio bearer at each UE”). Therefore, the UE needs to allocate the allocated resources among the radio bearers according to some rules. Unlike the case of HSUPA, the transport format is not selected on the UE side. The eNB determines the transport format based on some information (eg, reported scheduling information and QoS information) and the UE must follow the selected transport format. In HSUPA, the NodeB allocates the maximum uplink resources and the UE selects the actual transport format for data transmission accordingly.

Radio resource scheduling is the most important function in a shared channel access network in determining quality of service. Therefore, in order to enable efficient QoS management, requirements that the uplink scheduling scheme in LTE should satisfy are required. There are several.
・ The resource shortage of low priority services should be avoided.
• QoS should be clearly distinguished on individual radio bearers / services.
Allows fine-grained buffer reporting (eg, per radio bearer report or per radio bearer group report) in uplink reports so that the eNB scheduler can identify which radio bearer / service data is transmitted Should be.
• It should be possible to clearly distinguish QoS between the services of different users.
• It should be possible to provide a minimum bit rate for each radio bearer.

  As can be seen from the conditions listed above, one important aspect of LTE scheduling schemes is that operators control how their total cell capacity is distributed among individual radio bearers of different QoS classes. It is to provide a mechanism that can. The radio bearer QoS class is identified by the QoS profile of the corresponding SAE bearer signaled from the serving gateway to the eNB as described above. Operators can allocate a specific amount of their total cell capacity to the total traffic associated with a specific QoS class radio bearer. The main purpose of adopting this method based on class is to be able to distinguish the processing of packets according to the QoS class to which the packet belongs.

DRX (Discontinuous Reception)
In the case of RRC_IDLE, the DRX function can be set, in which case the UE uses either its own DRX value or the default DRX value (defaultPagingCycle). The default value is broadcast in the system information and can have 32, 64, 128, and 256 radio frames as values. If both the unique value and the default value are available, the UE selects the shorter of the two values. The UE needs to be activated in one paging opportunity per DRX cycle, and the paging opportunity is one subframe.

  The DRX function can also be set in the case of “RRC_CONNECTED”, so it is not always necessary to monitor the downlink channel. In order to prevent excessive consumption of the UE battery, 3GPP LTE (Release 8/9) and 3GPP LTE-A (Release 10) provide the concept of discontinuous reception (DRX). Chapter 5.7 of Non-Patent Document 2, which is a technical standard, describes DRX, which is incorporated herein by reference.

The following parameters are available for defining the DRX behavior of the UE: an on period when the mobile node is active and a period when the mobile node is in DRX mode.
-On period : A period (unit: downlink subframe) in which the PDCCH is received and monitored after the UE starts from DRX. When the UE successfully decodes the PDCCH, the UE maintains an activated state and activates an inactivity timer. [1 to 200 subframes, 16 steps: 1 to 6, 10 to 60, 80, 100, 200]
-DRX inactivity timer : A period (unit: downlink subframe) in which the UE waits for successful decoding of further PDCCHs after the last successful decoding of PDCCHs. The UE enters DRX again when it cannot successfully decode the PDCCH during this period. The UE restarts the inactivity timer after successfully decoding the PDCCH once for the first transmission only (ie not retransmission). [1-2560 subframes, 22 steps, 10 reserves: 1-6, 8, 10-60, 80, 100-300, 500, 750, 1280, 1920, 2560]
DRX retransmission timer : specifies the number of consecutive PDCCH subframes for which the UE expects downlink retransmissions after the first available retransmission time. [1 to 33 subframes, 8 steps: 1, 2, 4, 6, 8, 16, 24, 33]
-Short DRX cycle : Specifies a periodic repetition of an on period followed by an inactive period in a short DRX cycle. This parameter is optional. [2-640 subframes, 16 steps: 2, 5, 8, 10, 16, 20, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640]
-Short DRX cycle timer : Specifies the number of consecutive subframes that the UE follows the short DRX cycle after the DRX inactivity timer expires. This parameter is optional. [1-16 subframes]
-Long DRX cycle start offset : Specifies a periodic repetition in which an inactive period is followed by an inactive period in the long DRX cycle, and an offset (unit: subframe) when the on period starts (unit: subframe) Obtained by the formula defined in section 5.7). [Cycle length 10 to 2560 subframes, 16 steps: 10, 20, 30, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640, 1024, 1280, 2048, 2560. Offset is an integer between [0 and subframe length of selected cycle]

  The total period during which the UE is active is referred to as “active time”. The active time includes the duration of the DRX cycle, the time that the UE is continuously receiving while the inactivity timer has not expired, and the UE is waiting for downlink retransmission after 1 HRQ RTT. The time during which continuous reception is performed is included. Similarly, for the uplink, the UE is woken up in subframes that can receive the uplink retransmission grant (ie, every 8 ms after the first uplink transmission until the maximum number of retransmissions is reached). Based on the above, the minimum active time is equal in length to the on period and the maximum active time is undefined (infinite).

  The operation of DRX provides the mobile terminal with the opportunity to repeatedly deactivate the radio circuit (according to the DRX cycle currently in effect) for the purpose of saving power. It can be determined by the UE whether the UE actually remains in the DRX (ie inactive) state during the DRX period. For example, the UE normally performs an inter-frequency measurement, but this measurement cannot be performed during the on period and therefore needs to be performed at some other time during the DRX opportunity.

  When parameterizing a DRX cycle, there is a trade-off between battery saving and latency. For example, in the case of a web browsing service, it is usually a waste of resources for the UE to continuously receive the downlink channel while the user is reading a downloaded web page. A long DRX period is advantageous in extending the battery life of the UE. In contrast, a short DRX period is advantageous for responding faster than when data transmission is resumed (eg, when a user requests another web page).

  To satisfy these conflicting requirements, two DRX cycles (short cycle and long cycle) can be set for each UE. The short DRX cycle is optional, i.e. only the long DRX cycle is used. The transition between short DRX cycle, long DRX cycle, continuous reception is controlled by a timer or by an explicit command from the eNodeB. In a sense, the short DRX cycle can be regarded as a confirmation period before the UE enters the long DRX cycle when the packet arrives late. If data arrives at the eNodeB while the UE is in a short DRX cycle, scheduling to transmit that data is performed in the next on-period, and then the UE resumes continuous reception. On the other hand, if data does not arrive at the eNodeB during the short DRX cycle, the UE enters the long DRX cycle assuming that packet transmission has been completed for the time being.

  During the active time, the UE monitors the PDCCH, reports SRS (Sounding Reference Signal) (when set), CQI (Channel Quality Information) / PMI (Precoding Matrix Indicator) / RI (Rank Indicator) / PTI (Precoder Type Indication) is reported on PUCCH. When UE is not in active time, SRS (type-0-triggered SRS) of trigger type 0 and CQI / PMI / RI / PTI cannot be reported on PUCCH. When CQI masking is configured for the UE, CQI / PMI / RI / PTI reporting on PUCCH is limited to the on period.

  Available DRX values are controlled by the network and start from non-DRX up to x seconds. The value x may be the same length as the paging DRX used in RRC_IDLE. Measurement requirements and reporting criteria may vary according to the length of the DRX interval, i.e., with a long DRX interval, the requirement can be more relaxed (discussed in more detail later). When DRX is set, the UE can send periodic CQI reports only during “active time”. RRC can further constrain periodic CQI reports such that periodic CQI reports are sent only during the on period.

  FIG. 7 discloses an example of DRX. The UE is indicated by a scheduling message (C-RNTI (Cell-Radio Network Temporary Identity) on the PDCCH) during the “on period” of either the long DRX cycle or the short DRX cycle, depending on the cycle currently in effect. ) Is checked. When a scheduling message is received during the “on period”, the UE activates an “inactivity timer” and monitors the PDCCH in each subframe while the inactivity timer is running. During this period, the UE can be considered to be in continuous reception mode. If a scheduling message is received while the inactivity timer is running, the UE restarts the inactivity timer, and when the inactivity timer expires, the UE transitions to the short DRX cycle and the “short DRX cycle timer” ". A short DRX cycle can also be initiated by the MAC control element. When the short DRX cycle timer expires, the UE transitions to a long DRX cycle.

  In addition to this DRX behavior, a “HARQ Round Trip Time (RTT) Timer” is defined for the purpose of allowing the UE to sleep during HARQ RTT. If the decoding of the downlink transport block in one HARQ process fails, the UE may assume that the next retransmission of that transport block will occur at least after the “HARQ RTT” subframe. While the HARQ RTT timer is running, the UE does not need to monitor the PDCCH. When the HARQ RTT timer expires, the UE resumes receiving PDCCH as usual.

  There is only one DRX cycle per UE. All aggregated component carriers follow this DRX pattern.

Uplink power control Uplink transmit power control in mobile communication systems serves an important purpose. Uplink transmit power control minimizes the need to transmit enough energy per bit to achieve the required quality of service (QoS), interference with other users of the system, and Balance between the need to maximize battery life. In achieving this goal, the role of power control (PC) is crucial in controlling the interference caused to neighboring cells while providing the required SINR. In the idea of the classic power control scheme in the uplink, all users receive with the same SINR (known as full compensation). Instead, 3GPP adopted the use of fractional power control (FPC) in LTE. With this new feature, users with high path loss operate with low SINR requirements, and in many cases, there is less interference caused to neighboring cells.

  In LTE, detailed power control expressions are specified for PUSCH (Physical Uplink Shared Channel), PUCCH (Physical Uplink Control Channel), and SRS (Sounding Reference Signal). (See Section 5.1 of Non-Patent Document 3) (available on the 3GPP website and incorporated herein by reference). The power control equation for each of these uplink signals follows the same basic principle. In either case, the power control equation is derived from two main terms: the static or semi-static parameters signaled by the eNodeB, the basic operating point of the open loop, and the dynamic updated every subframe. It can be considered as the sum of offset (correction).

The basic open-loop operating point for determining the transmission power per resource block depends on multiple factors such as inter-cell interference and cell load. The basic operating point of the open loop is further divided into two elements: a semi-static basic level P ₀ (consisting of a common power level (measurement unit: dBm) of all UEs in the cell and a UE-specific offset). Can be broken down into open loop path loss compensation elements. The dynamic offset part of the power per resource block is further divided into two elements, an element that depends on the modulation and coding scheme (MCS), and an explicit Transmit Power Control (TPC) command. Can be disassembled.

Modulation and (called the delta _TF in the LTE specification, TF is the representative of "transport format") coding scheme dependent elements, be adapted according to the data rate of the information that the transmission power per resource block are transmitted it can.

  Another element of the dynamic offset is a UE specific transmit power control (TPC) command. This command operates in two modes: cumulative TPC (accumulative TPC) command (available for PUSCH, PUCCH, and SRS) and absolute TPC command (available only for PUSCH). be able to. Switching between these two modes for PUSCH is set semi-statically by RRC signaling per UE (ie, the mode cannot be changed dynamically). For cumulative TPC commands, each TPC command signals a power step relative to the previous level.

Power Headroom Reporting In order to assist the eNodeB in appropriately scheduling uplink transmission resources for multiple UEs, it is important that the UE can report available power headroom to the eNodeB.

  The eNodeB may determine further uplink bandwidth per subframe that the UE can use using power headroom reporting. This serves to avoid resources being allocated to UEs that cannot use uplink transmission resources in order to avoid wasting resources.

  The range of power headroom reports is +40 to −23 dB (see Section 9.1.8.4 of Non-Patent Document 4) (available on the 3GPP website, which is hereby incorporated by reference in its entirety. Built in). The negative part of the range can signal the degree of power shortage to the eNodeB when the uplink grant received by the UE requires more transmit power than it can use. As a result, the base station can reduce the size of the next grant, and the transmission resource is released and allocated to another UE.

  The power headroom report can only be sent in subframes where the UE has an uplink transmission grant. The report relates to the subframe that is sent. Thus, headroom reporting is a prediction, not a direct measurement. The UE cannot directly measure the actual transmit power headroom of the subframe in which the report is transmitted. Thus, headroom reporting relies on the UE power amplifier output calibration being sufficiently accurate.

The following are defined as multiple criteria for triggering power headroom reporting:
− The estimated path loss has changed significantly since the last power headroom report.
− More than the set time has elapsed since the last power headroom report.
-More than the configured number of closed loop TPC commands have been executed by the UE.

  The eNodeB can set parameters for controlling each of these triggers according to the system load status and the scheduling algorithm requirements. Specifically, RRC sets two timers (power headroom reporting periodic timer (periodicPHR-Timer) and power headroom reporting prohibition timer (prohibitPHR-Timer)), and changes in measured downlink path loss. The power headroom report is controlled by triggering the power headroom report by signaling dl-PathlossChange indicating

  The power headroom report is sent as a MAC control element. The MAC control element consists of 1 octet, the upper 2 bits are reserved, and the lower 6 bits represent the above-mentioned 64 dB value (1 dB interval). FIG. 8 shows the structure of the Release 8 power headroom report MAC control element.

The effective power headroom PH [dB] of the UE in subframe i is defined by the following equation (refer to section 5.1.1.2 of Non-Patent Document 3).
_{PH (i) = P CMAX -} {10log 10 (M PUSCH (i)) + P 0_PUSCH (j) + a (j) · PL + Δ TF (i) + f (i)} ( Equation 1)
The power headroom is rounded to the nearest value in the range [40; -23] dB (1 dB interval). P _CMAX is the maximum total UE transmission power (or the maximum total transmission power of the UE), and is a value selected by the UE based on the following constraints within a predetermined range of P _{CMAX_L to} P _{CMAX_H} .
P _{CMAX_L} ≦ P _CMAX ≦ P _{CMAX_H}

P _{CMAX_L} = min (P _EMAX −ΔT _C , P _PowerClass −MPR−AMPR−ΔT _C )

P _{CMAX_H} = min (P _EMAX , P _PowerClass )
P _EMAX is a value that is signaled by the network, MPR, AMPR (also denoted AMPR), and [Delta] T _C is, ΔT _C, MPR, and AMPR (additional maximum power reduction: Additional Maximum Power Reduction, (Also referred to as A-MPR) is defined in Section 6.2 of Non-Patent Document 5 (available on the 3GPP website and incorporated herein by reference).

  MPR is a power reduction value (so-called maximum power reduction) and is used to control ACLR (Adjacent Channel Leakage Power Ratio) associated with various modulation schemes and transmission bandwidths.

A-MPR is an additional maximum power reduction. This value is band specific and applies when set by the network. Therefore, P _cmax is specific to the UE implementation and is therefore not known to the eNB.

Uplink power control in carrier aggregation One key point of uplink power control in LTE-Advanced is that uplink power control specific to the component carrier is supported, i.e. the uplink components configured for the user. There is one independent power control loop for each carrier. Furthermore, power headroom is reported for each component carrier.

In Release 10, within the range of carrier aggregation, there are two types of maximum power limits: the maximum total UE transmission power and the maximum transmission power specific to the component carrier. RAN1 agreed at the # 60bis meeting that the power headroom report reported for each component carrier considers maximum power reduction (MPR). In other words, the power reduction applied by the UE is taken into account in the maximum transmission power P _{CMAX, c} (c represents the component carrier) specific to the component carrier. As already mentioned above, the purpose of MPR / A-MPR allows a mobile terminal to reduce its maximum transmit power so that it can meet the requirements regarding signal quality, spectral emission mask, and spurious emission. It is to be.

  As already mentioned above, the purpose of the value MPR / A-MPR allows the mobile terminal to reduce its maximum transmit power so that the requirements for signal quality, spectral emission mask and spurious emission can be met. Is to do.

  In Release 10, in addition to MPR and A-MPR, the objective is to consider multi-RAT terminals that have to limit their LTE total output power, especially when simultaneous transmission with another RAT (Radio Access Technology) takes place So-called power management MPR (also referred to as P-MPR) was introduced. Such power limitations are due, for example, to restrictions on the specific absorption rate (SAR) of radio energy into the user's body and out-of-band emission requirements that can be affected by inter-modulation products of simultaneous radio transmissions. Can occur. P-MPR is not summed with MPR / A-MPR, because reducing the maximum output power of the UE against the latter factor helps to meet the requirements that require P-MPR. .

Thus, the UE sets its nominal maximum transmit power P _CMAX (ie, the maximum transmit power available at the UE) according to the following equation, taking into account additional power management MPR (P-MPR).
P _{CMAX_L} ≦ P _CMAX ≦ P _{CMAX_H}

P _{CMAX_L} = MIN {P _EMAX −ΔT _C , P _PowerClass −max (MPR + A−MPR, P−MPR) −ΔT _C }

P _{CMAX_H} = MIN {P _EMAX , P _PowerClass }

In the case of carrier aggregation, P _CMAX becomes P _{CMAX, c} (maximum transmission power unique to the component carrier). Essentially, the maximum output power set for the serving cell c is set within the following range.
P _{CMAX_L, c} ≦ P _{CMAX, c} ≦ P _{CMAX_H, c}

Two different aggregation schemes are considered, in one scheme, the aggregated carriers are in the same frequency band, and in the other scheme, carriers in different frequency bands are aggregated.
For continuous carrier aggregation in the same frequency band:
P _{CMAX_L, c} = MIN {P _{EMAX, c} −ΔT _{C, c} , P _PowerClass −MAX (MPR _c + A−MPR _c + ΔT _{IB, c} , P−MPR _c ) −ΔT _{C, c} }
For carrier aggregation in different frequency bands:
P _{CMAX_L, c} = MIN {P _{EMAX, c} −ΔT _{C, c} , P _PowerClass −MAX (MPR _c + A−MPR _c + ΔT _{IB, c} , P−MPR _c ) −ΔT _{C, c} }

P _{CMAX_H, c} = MIN (P _{EMAX, c} , P _PowerClass )
P _{EMAX, c} is a value given by IE P-Max of the serving cell c in Non-Patent Document 6.

In the case of different frequency band carrier aggregation, MPR _c and A-MPR _c are applied to each serving cell c, that is, there is a separate MPR and A-MPR for each serving cell. In the case of continuous carrier aggregation in the same frequency band, MPR _c = MPR and A-MPR _c = A-MPR. P-MPR _c is a power management term for the serving cell c. In the case of continuous carrier aggregation in the same frequency band, there is one power management term P-MPR for the UE, and P-MPR _c = P-MPR.

In the case of carrier aggregation including two uplink serving _cells , the set maximum total output power P _CMAX is set within the following range.
P _{CMAX_L_CA} ≦ P _CMAX ≦ P _{CMAX_H_CA}
For continuous carrier aggregation in the same frequency band:
P _{CMAX_L_CA} = MIN {10 · log ₁₀ Σp _{EMAX, c} −ΔT _C , P _PowerClass −MAX (MPR + A−MPR + ΔT _{IB, c} , P−MPR) −ΔT _C }

P _{CMAX_H_CA} = MIN {10 · log ₁₀ Σp _{EMAX, c} , P _PowerClass }
_Where p _{EMAX, c} is the linear value of P _{EMAX, c} given by RRC signaling (see Non-Patent Document 6 incorporated herein by reference for details).
In the case of different frequency band carrier aggregation including a maximum of one serving cell c for each operating band:
P _{CMAX_L_CA} = MIN {10 · log ₁₀ ΣMIN [p _{EMAX, c} / (Δt _{C, c} ), p _PowerClass / (mpr _c · a−mpr _c · Δt _{C, c} · Δt _{IB, c} ), p _PowerClass / ( p-mpr _c · Δt _{C, c} )], P _PowerClass }

P _{CMAX_H_CA} = MIN {10 · log ₁₀ Σp _{EMAX, c} , P _PowerClass }
In the equation, p _{EMAX, c} is a linear value of P _{EMAX, c} given by Non-Patent Document 6. MPR _c and A-MPR _c are applied to each serving cell c, and are defined in Sections 6.2.3 and 62.4 of Non-Patent Document 5 (incorporated herein by reference), respectively. Has been. mpr _c is a linear value of MPR _c , and a-mpr _c is a linear value of A-MPR _c . P-MPR _c considers the power management of serving cell c. p-mpr _c is a linear value of P-MPR _c .

  Further details regarding the definition of the maximum transmission power specific to the component carrier or the maximum total transmission power of the UE are given in Non-Patent Document 5 (incorporated herein by reference).

  Unlike Release 8/9, for LET-A, the UE must also handle simultaneous transmission of PUSCH and PUCCH, multi-cluster scheduling, and simultaneous transmission on multiple component carriers, In comparison with Release 8/9, a large MPR value is required, and the variation of the applied MPR value is large.

Note that the eNB is not aware of the power reduction applied by the UE for each component carrier, because the actual power reduction depends on the type of allocation, the standardized MPR value, and even the UE implementation. It is to do. Therefore, the eNB does not recognize the maximum transmission power specific to the component carrier that is a reference when the UE calculates the PHR. In Release 8/9, for example, the maximum transmit power P _cmax of the UE may be within some specific range as described above.
P _{CMAX_L} ≦ P _CMAX ≦ P _{CMAX_H}

Since the power reduction applied by the UE to the component carrier's maximum transmit power is not recognized by the eNB, a new power headroom MAC control element (also called extended power headroom MAC control element) is introduced in Release 10 Agreed to do. As a major difference from the format of the power headroom (PHR) MAC control element in Release 8/9, the new power headroom includes a Release 8/9 power headroom value for each active uplink component carrier. Thus, the new power headroom is of variable size. Furthermore, the new power headroom reports not only the component carrier power headroom value, but also the corresponding P _{cmax, c} (maximum transmission power of the component carrier with index c). For the purpose of considering the simultaneous transmission of PUSCH and PUCCH, the UE reports the Release 8/9 power headroom value (referred to as Type 1 power headroom) related to the PUSCH-only transmission for the PCell, and the UE If configured to support simultaneous transmission of PUSCH and PUCCH, it reports additional power headroom values (also referred to as Type 2 power headroom) that take into account the transmission of PUCCH and PUSCH.

In order to enable the eNB to recognize whether the maximum transmission power has been reduced due to MPR / A-MPR power reduction or due to the application of P-MPR, 1 bit in the extended power headroom MAC CE Indices (also referred to as P bits) have been introduced. More specifically, if power backoff (P-MPR) by power management is not applied, if the corresponding maximum transmission power (P _{CMAX, c} ) has a different value, the UE sets P = 1. To do. In essence, this P bit is used by the eNB to delete PHR reports affected by the P-MPR from the MPR-learning algorithm at the eNB, i.e., the eNB uses a specific resource allocation. The MPR value used by the UE is stored in the internal table.

  For further details regarding the extended power headroom MAC control element shown in FIG. 9, see, for example, 6.1. Of Non-Patent Document 2 (available on the 3GPP website and incorporated herein by reference). See section 3.6a.

Type 1 power headroom can also report on subframes in which no PUSCH is actually transmitted. This special PHR is also referred to as a virtual PHR. In such a case, ₁₀ log ₁₀ (M _PUSCH (i)) and Δ _{TF, c} (i) in the power headroom reporting equation shown above are set to zero. The value of the path loss (PL), the value of the received TPC command f (i), and the values of other constants specific to the component carrier (P _{0_PUSCH} (j), a) are the same even when uplink data transmission is not performed. Also, it can be determined for the uplink component carrier.
PH _{virtual, c} (i) = P _{CMAX, H, c} − {P 0 _—PUSCH (j) + a (j) + PL _c + f (i)}

This value is the power headroom assuming a default transmission setting corresponding to the minimum resource allocation (M = 1) and the modulation and coding scheme associated with Δ _{TF, c} (i) = 0 dB Can be considered.
The maximum transmission power P ~ _{CMAX, c} (i) specific to the carrier is calculated assuming the following.
MPR = 0dB
A-MPR = 0dB
P-MPR = 0dB
ΔT _C = 0 dB
In essence, P _{CMAX, c} (i) is equal to P _{CMAX_H, c} = MIN {P _{EMAX, c} , P _PowerClass }.

Similar to Type 1 power headroom reporting, Type 2 power headroom may report on subframes in which one or both of the PUSCH PUCCHs are not transmitted. In this case, minimum resource allocation (M = 1) and ΔMCS = 0 dB for PUSCH and h (n _CQI , nH _ARQ , n _SR ), Δ _{F_PUCCH} (F), Δ set to 0 for PUCCH Assuming _TxD (F ′), the virtual transmission power of PUSCH and / or PUCCH is calculated. Further details regarding the calculation of power headroom can be found in Non-Patent Document 3, which is incorporated herein by reference.

With the explosive demand for small cell mobile data, mobile operators are changing the strategies needed to meet the difficult demands of higher capacity and improved user experience quality (QoE). Currently, a fourth generation wireless access system using LTE is being deployed by many operators around the world to provide faster access with lower latency and higher efficiency than 3G / 3.5G systems. is there. Nevertheless, the expected future traffic growth is enormous, especially in high traffic areas (hot spot areas) where the greatest amount of traffic occurs, making the network even higher to handle the required capacity. The need for densification is greatly increased. Increased network density (reduces the physical distance from user terminals to network nodes by increasing the number of network nodes) increases traffic capacity and increases the achievable user data rate of wireless communication systems It is a policy to hold the key.

  Network densification, in addition to simply densifying the deployment of macro nodes, is supplemented by low-power auxiliary (low-power) nodes under the coverage of the existing macro-node layer. node) or small cells can be achieved. When deploying such different types of nodes, low power nodes provide very high traffic capacity and very high user throughput locally (eg, in indoor and outdoor hotspot areas). On the other hand, the macro layer ensures service availability and QoE throughout the coverage area. In other words, the layer containing the low power nodes can provide local area access as opposed to the macro layer covering a large area.

  The installation of low power nodes or small cells and the deployment of different types of nodes are possible from the initial release of LTE. In this regard, a number of solutions are defined in the recent release of LTE (ie release 10/11). More specifically, these releases introduced additional strategies and features to deal with inter-layer interference when different types of nodes are deployed. In order to further optimize performance and provide cost and energy efficient operation, small cells require further enhancements and often interact with or assist macro cells. There is a need to. Such a solution will be considered in further evolution after LET Release 12. In particular, further enhancements related to the deployment of low-power nodes and different types of nodes are under the new Release 12 Study Item (SI), “Study on Small Cell Enhancements for E-UTRA and E-UTRAN”. To be considered. Some of these considerations focus on achieving higher levels of interworking between the macro and low power layers, such as the macro layer supporting the low power layer and dual layer connectivity in various ways. Is applied. Dual connectivity means that the device connects to both the macro layer and the low power layer simultaneously.

  The following describes some of the deployment scenarios envisioned in this Study Item for small cell enhancements. In the following scenario, a backhaul technology classified as non-ideal backhaul in Non-Patent Document 7 is assumed.

  Ideal backhaul (ie, backhaul with very high throughput and low latency, such as a dedicated point-to-point connection using fiber optics) and non-ideal backhaul (ie, xDSL, microwave, other backhaul ( Both general backhaul (eg widely used in the market), eg relay), should be considered. In this case, the trade-off between performance and cost should be considered.

The following table shows the classification of non-ideal backhaul based on information from operators.

  This Study Item does not assume fiber access that can be used to deploy a remote radio head (RRH). The home base station (HeNB) is not excluded, but is not distinguished from the pico base station in terms of deployment scenarios and challenges, even if the transmission power of the home base station is lower than the transmission power of the pico base station (Pico eNB). The following three scenarios are considered.

  Scenario 1 is shown in FIG. 10 and is a deployment scenario in which a macro cell and a small cell having the same carrier frequency (same frequency) are connected via a non-ideal backhaul. Users are distributed both outdoors and indoors.

  Scenario 2 is shown in FIG. 11 and FIG. 12, and is a deployment scenario in which macrocells and small cells having different carrier frequencies (different frequencies) are connected via a non-ideal backhaul. Users are distributed both outdoors and indoors. There are essentially two different scenarios 2 (referred to herein as scenario 2a and scenario 2b), with the difference being that indoor deployment of small cells is considered in scenario 2b.

  Scenario 3 is shown in FIG. 13 and is a deployment scenario in which only small cells of one or more carrier frequencies are connected via a non-ideal backhaul link.

  There are different challenges / problems that need to be considered further for each deployment scenario. Such problems in each deployment scenario are recognized at the Study Item stage, and are described in Non-Patent Document 8. Refer to this non-patent document 8 for further details on these issues / problems.

In order to solve the recognized problems described in Section 5 of Non-Patent Document 8, this Study Item considers the following design goals in addition to the requirements specified in Non-Patent Document 7 .
Regarding the robustness (robustness) of mobility:
-For UEs in RRC_CONNECTED state, the mobility performance achieved by small cell deployment should be comparable to the mobility performance in a macro cell only network.
Regarding the increase in signaling load due to frequent handovers:
-New solutions should ensure that the signaling load towards the core network does not result in excessive increase. However, additional signaling load and user plane traffic load due to small cell enhancements should also be considered.
For improved throughput and system capacity per user:
-The goal should be to utilize radio resources across macro and small cells in order to achieve per-user throughput and system capacity close to ideal backhaul deployments, taking into account QoS requirements. is there.

One promising solution to the problem currently under consideration in the dual connectivity 3GPP RAN working group is the so-called “dual connectivity” concept. The term “dual connectivity” means an operation in which one UE consumes radio resources provided by at least two different network nodes connected via a non-ideal backhaul. In essence, the UE is connected to both a macro cell (macro eNB) and a small cell (secondary eNB or small eNB). Further, each eNB involved in UE dual connectivity can play a different role. These roles do not necessarily depend on the power class of the eNB and may be different for each UE.

The Study Item is currently in a very early stage, so details about dual connectivity have yet to be determined. For example, the architecture has not yet been agreed. Thus, many issues / details (eg protocol enhancements) are still undecided at this time. FIG. 14 illustrates an exemplary architecture for dual connectivity. However, it should be understood that this architecture is only one possible option. The present disclosure is not limited to this particular network / protocol architecture and can be applied more generally. In this specification, the following is assumed regarding the architecture.
-Decide the cell to process each packet at the bearer level and split the control plane and user plane. As an example, RRC signaling to the UE and high QoS data such as VoLTE can be processed by the macro cell, and best effort data is processed by the small cell.
-No connection between bearers. Therefore, common PDCP and RLC are not required between the macro cell and the small cell.
-Coordination between RAN nodes is loose.
-The small eNB (SeNB) does not connect to the serving gateway (S-GW) (ie the packet is forwarded by the macro eNB (MeNB)).
-Small cells are transparent to the core network (CN).

Note that with respect to the last two assumptions, it is also possible for the small eNB to connect directly to the serving gateway (ie, S1-U is between the serving gateway and the small eNB). There are essentially three different options for bearer mapping / partitioning:
Option 1: S1-U also terminates in the small eNB (shown in FIG. 15A).
-Option 2: S1-U terminates in the macro eNB and bearers are not split within the RAN (shown in FIG. 15B).
-Option 3: S1-U terminates in the macro eNB and the bearer is split in the RAN (shown in FIG. 15C).

  15A-15C show three options for the downlink direction of user plane data as an example. For the purpose of illustration, option 2 is primarily assumed in the present application, and FIG.

  In addition to considering user plane data partitioning as shown in FIGS. 15A-15C, various alternatives are also being considered for user plane architecture.

  As a common recognition, when the S1-U interface terminates in the macro eNB (FIGS. 15B, 15C), the protocol stack in the small eNB must support at least RLC (re) segmentation. For this reason, RLC (re) segmentation is an operation closely related to the physical interface (eg, the MAC layer indicates the size of the RLC PDU) (see above)) and non-ideal backhaul is used. This is because RLC (re) segmentation must be performed at the same node that transmits the RLC PDU.

Disadvantages of prior art power control As explained in the previous section, small cell and dual connectivity have just been developed recently and there are several issues that need to be addressed to enable an efficient system. Still exists.

  In the dual connectivity scenario described above, Release 12 supports simultaneous uplink transmission (also referred to as dual transmission) from the UE to both the macro eNB and the small eNB. There are two independent schedulers (one scheduler belonging to the macro eNB and the other belonging to the small eNB), and each scheduler schedules uplink transmission of the UE independently of each other. More specifically, the uplink resource allocation scheduled in one cell is not recognized in the other cell. In other words, the macro eNB scheduler does not recognize the uplink scheduling decision made by the small eNB, and vice versa.

  For this reason, there is an increased probability that the UE's power will be limited (ie exceeding the UE's maximum total transmit power when two uplink transmissions with too much power are scheduled).

  This is illustrated in FIG. 16, which shows that two uplink transmissions (one for the macro eNB and one for the small eNB) are scheduled for the UE and the power is Indicates a restricted situation. As is apparent from the figure, this simultaneous uplink transmission exceeds the maximum total transmit power of the UE, so that the UE uses a total power used for two uplink transmissions that is greater than the maximum total transmit power of the UE. Power scaling is performed on these uplink transmissions so that they are kept low. Such power scaling reduces scheduling efficiency and performance.

3GPP TS 36.211, "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation", version 8.9.0 3GPP TS 36.321, "Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocol specification", version 10.0.0 3GPP TS 36.213, "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures", version 8.8.0 3GPP TS 36.133, "Requirements for support of radio resource management", version 8.7.0 3GPP TS 36.101, "Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) radio transmission and reception", version 8.7.0 TS36.331 TR 36.932 TR 36.842

  An exemplary embodiment that does not limit the present invention avoids the above-mentioned problems of the prior art in a mobile communication system in which the mobile station is in a dual connectivity state with a master base station and a secondary base station. An improved method of power control is provided. Another exemplary embodiment provides a power headroom reporting method to support improved power control in the case of dual connectivity scenarios.

  Further benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. These benefits and advantages can be provided individually by the various embodiments and features disclosed in this specification and the drawings, and need not all be provided to obtain one or more of these benefits and advantages. .

  In one general aspect, the technique disclosed in the present specification is an integrated circuit that controls a mobile station capable of power headroom reporting in a mobile communication system, and the mobile station uses a first radio link. The first radio between the mobile station and the master base station is connectable to a master base station via a second radio link and is connectable to at least one secondary base station via a second radio link. A process of calculating a first power headroom report of a link by the mobile station; and calculating the calculated first power headroom report to the second radio link between the mobile station and the secondary base station. A process for transmitting information from the mobile station to the master base station, together with information that enables the master base station to determine information on the path loss of the mobile station, and A second power headroom report of the second radio link to the Dali base station is calculated by the mobile station, and the calculated second power headroom report is transmitted from the mobile station to the secondary base station. And an integrated circuit that controls processing to be transmitted.

  This general aspect can be implemented by a system, device, and computer program, or by any combination of system, device, computer program.

1 illustrates an exemplary architecture of a 3GPP LTE system. 1 illustrates an exemplary overview of the entire 3GPP LTE E-UTRAN architecture. Fig. 3 illustrates an exemplary subframe boundary of a downlink component carrier as defined in 3GPP LTE (Release 8/9). Fig. 4 shows an exemplary downlink resource grid of downlink slots defined in 3GPP LTE (Release 8/9). 3 shows a layer 2 structure of 3GPP LTE-A (Release 10) in a state where downlink carrier aggregation is enabled. 3 shows a layer 2 structure of 3GPP LTE-A (Release 10) in a state where uplink carrier aggregation is enabled. It shows the DRX operation of the mobile terminal, and in particular the DRX opportunity and the on period due to the short DRX cycle and the long DRX cycle. Fig. 3 illustrates a MAC control element of a power headroom report (PHR) as defined in 3GPP LTE (Release 8/9). Fig. 2 illustrates the MAC control element of the Extended Power Headroom Report (ePHR) defined in 3GPP LTE (Release 10). As a deployment scenario for enhancing the function of a small cell, a case where a macro cell and a small cell use the same carrier frequency is shown. As a further deployment scenario for enhancing the function of the small cell, the case where the macro cell and the small cell use different carrier frequencies and the small cell is outdoors is shown. As a further deployment scenario for enhancing the function of the small cell, a case is shown in which the macro cell and the small cell use different carrier frequencies and the small cell is indoors. The case where only a small cell is provided is shown as a further deployment scenario for enhancing the function of the small cell. The outline | summary of the communication system architecture in the double connection by which macro eNB and small eNB are connected to a core network is shown, and it is a case where a S1-U interface terminates in macro eNB and a bearer is not divided | segmented within RAN. A number of different options are shown when having two separate EPS bearers between the serving gateway and the UE. A number of different options are shown when having two separate EPS bearers between the serving gateway and the UE. A number of different options are shown when having two separate EPS bearers between the serving gateway and the UE. FIG. 2 shows a scenario in which power is limited in the prior art, where a UE is connected to both a macro eNB and a small eNB, and each of the macro eNB and the small eNB sets the output power of the UE for uplink transmission to itself. This is the case of independent control. FIG. 6 illustrates a situation where initial values of power parameters P _{EMAX, MeNB} and P _{EMAX, SeNB} are delivered from a macro eNB to a small eNB and UE according to an alternative embodiment. FIG. 6 illustrates a situation where initial values of power parameters P _{EMAX, MeNB} and P _{EMAX, SeNB} are delivered from a macro eNB to a small eNB and UE according to another alternative embodiment. FIG. 6 illustrates a situation where initial values of power parameters P _{EMAX, MeNB} and P _{EMAX, SeNB} are delivered from a macro eNB to a small eNB and UE according to yet another alternative embodiment. According to one embodiment of the present disclosure shows a structure of a MAC control element of the power headroom reporting (CE), the MAC control element _{informs P EMAX,} virtual _{P CMAX} is the same as the _SeNB, the _SeNB Small eNB In addition to the extended power headroom report for the second radio link, the virtual power headroom report for the second radio link and the virtual _{PCMAX, SeNB} are further included. FIG. 6 illustrates a modified improved power headroom reporting method performed by a UE according to one embodiment of the present disclosure, wherein an extended power headroom report for a second radio link is transmitted to a small eNB, In addition to the extended power headroom report of the first radio link, a virtual power headroom report of the second radio link is further transmitted in order to inform the macro eNB of the path loss. FIG. 22 shows a structure of a power headroom reporting MAC control element according to an embodiment of the present disclosure, which may be used in connection with the PHR transmission of FIG. Extended power headroom reports and a second wireless link virtual power headroom report. FIG. 22 shows the structure of a MAC control element of the power headroom report for the second radio link, which can be used in connection with the PHR transmission of FIG. 21, ie, an extension of the second radio link. Includes power headroom report.

  In the following, it is assumed that the mobile station is in a dual connectivity state and is therefore connected to both the master base station and the secondary base station via respective radio links. As explained above, one of the problems associated with this assumed scenario is that the two schedulers at the master base station and the secondary base station schedule mobile station uplink transmissions independently of each other. As a further problem, the master base station and the secondary base station also independently control the power used by the mobile station for uplink transmission to these base stations. The purpose of avoiding the power limited situation illustrated in FIG. 16 (ie, the mobile station needs to perform power scaling to reduce its power output to be within its power output limits). Thus, the present disclosure proposes as follows.

  According to the first aspect of the present disclosure, the power control of the mobile station is controlled mainly by a single base station (master base station or secondary base station). In the following, for illustrative purposes only, it is assumed that the power control according to this first aspect of the present disclosure is performed by the master base station and not by the secondary base station. Of course, this first aspect of the present disclosure is also applied to a scenario in which the base station that controls the power of the mobile station is a secondary base station, with corresponding changes being made.

  Therefore, the master base station is responsible for distributing the maximum output power that the mobile station can use for uplink transmission between uplink transmission to the master base station and uplink transmission to the secondary base station. The ratio of power distribution between two base stations can be defined by taking into account various parameters of the base station and the intended communication, in which case the parameters are e.g. from the mobile station to the two base stations One or more of: path loss on the radio link to, traffic load on the two base stations, resources available on the two radio links to the two base stations.

  Information about the path loss can be determined at the master base station, eg, by measurement or by receiving a virtual power headroom report (see later description). The load information is received directly from the secondary base station, or the master base station derives from the received buffer status report targeting the radio bearer of the secondary base station.

  The power distribution ratio is, for example, 50% of the maximum output power of the mobile station for uplink transmission to the master base station, and the remaining 50% of the maximum output power of the mobile station for uplink transmission to the secondary base station. It can be. Of course, any other power distribution ratio (eg 40:60, 75:25, etc.) is also possible.

Thus, the master base station has two parameters: 1) the maximum output power of the mobile station for uplink transmission to the master base station (P _{EMAX, MeNB} ), and 2) uplink transmission to the secondary base station. The maximum output power (P _{EMAX, SeNB} ) of the trusted mobile station is determined. These parameters are used by the mobile station when performing an uplink transmission to each base station.

  When these parameters are determined, the parameters are notified to other entities (that is, secondary base stations and mobile stations). This step can be performed in a number of ways, some of which are specifically disclosed below.

According to a first alternative method, the master base station performs the steps for notifying the secondary base station and the mobile station of the necessary parameters, i.e. 1) the mobile station determined for uplink transmission to the secondary base station The maximum output power (P _{EMAX, SeNB} ) of the mobile station is transmitted from the master base station to the secondary base station, and 2) The maximum output power of the mobile station (P _{EMAX, SeNB} ) determined for uplink transmission to the secondary base station 3) Transmit the maximum output power (P _{EMAX, MeNB} ) of the mobile station determined for uplink transmission to the master base station from the master base station to the mobile station.

According to the second alternative method, the master base station transmits the maximum output power (P _{EMAX, SeNB} ) of the mobile station determined for uplink transmission to the secondary base station to the secondary base station, and sends it to the master base station. The maximum output power (P _{EMAX, MeNB} ) of the mobile station determined for uplink transmission is transmitted to the mobile station. Next, unlike the first alternative method, the secondary base station transmits the maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station received from the master base station to the mobile station. Forward.

According to a further third alternative, the master base station determines the maximum output power of the mobile station (P _{EMAX, SeNB} ) determined for uplink transmission to the secondary base station and for uplink transmission to the master base station. Both of the determined maximum output powers (P _{EMAX, MeNB} ) of the mobile station are transmitted to the mobile station. Next, the mobile station provides the secondary base station with information on the maximum output power (P _{EMAX, SeNB} ) of the mobile station determined for uplink transmission to the secondary base station. This step can be done in various ways, for example as a separate parameter associated with the power headroom report for the second radio link or as part of the virtual power headroom report for the second radio link, (It will be explained in more detail later).

  In either case, the two base stations and the mobile station can obtain information regarding power distribution and thus perform power control with minimal risk of power limiting situations, because This is because uplink scheduling and power control are performed by the base station so as not to exceed the maximum available output power of the mobile station.

  According to a further refinement related to this first aspect, the power distribution ratio initially defined by the master base station is monitored and updated (if necessary). In particular, the mobile station provides the necessary information related to this to the master base station responsible for controlling the power distribution. As already mentioned above, one basis on which the master base station determines the power distribution ratio is related to the path loss in the radio link between the mobile station and the master base station and between the mobile station and the secondary base station. Information. Accordingly, the mobile station assists the master base station to update the power distribution ratio by providing appropriate information regarding the path loss to the master base station.

  Initially, the master base station determines information about path loss on the first radio link between the mobile station and the master base station from the normal power headroom report for the first radio link received from the mobile station. can do. The power headroom value in the power headroom report is calculated by the mobile station based on information about the path loss on the first radio link to the master base station, so that the master base station relates to the path loss on the first radio link. This information can be derived from the received power headroom value. Furthermore, path loss information can be derived from the mobility measurement report (that is, RSRP / RSRQ measurement) of the first radio link provided to the master base station.

  Furthermore, corresponding information regarding the path loss in the second radio link between the mobile station and the secondary base station is provided to the master base station. Note the following points regarding this step: That is, by the power headroom report of the second radio link between the mobile station and the secondary base station transmitted by the mobile station to the secondary base station, the secondary base station obtains information on the path loss in the second radio link. Although it can be determined, the master base station cannot determine this information. This is because, unlike the secondary base station, the master base station is not aware of the resource allocation on which the mobile station calculates the power headroom report for the second radio link.

  On the other hand, the virtual power headroom report for the second radio link is a virtual uplink resource allocation that is set in advance for the second radio link to the secondary base station. To be determined by the mobile station based on (which is also known to the master base station). Therefore, this virtual power headroom report allows the master base station to determine information regarding the path loss of the second radio link.

  Thus, according to one refinement of the first aspect, rather than transmitting information about path loss in the second radio link directly from the mobile station to the master base station, the mobile station Assisting the master base station to determine and update power distribution by calculating a virtual power headroom report and sending it to the master base station. The secondary virtual power headroom report (ie, the virtual power headroom report for the second radio link), along with the “normal” power headroom report for the first radio link between the mobile station and the master base station, To the master base station.

  Thus, according to this refinement of the first aspect of the present disclosure, the power headroom reporting method performed by the mobile station is modified and improved as follows: the mobile station has the first radio link and the second radio link Power headroom reports for the first radio link to the master base station and the power headroom report for the second radio link to the secondary base station. ) In addition, the mobile station computes a virtual power headroom report for the second radio link and combines it with the “normal” power headroom report for the first radio link (ie in the same message). ) To the master base station.

In the above description, the expression “power headroom report” for the second radio link or the first radio link preferably means an extended power headroom report, where the extended power headroom report represents the power headroom value. In addition, the cell-specific maximum output power (P _{CMAX, MeNB} / P _{CMAX, SeNB} ) (defined by 3GPP) set by the mobile station for uplink transmission from the mobile station to the master base station / secondary base station And similar to _{PCMAX, c} described in the background section).

As a result, the master base station is provided with the necessary information regarding the path loss on both radio links. Therefore, the master base station can adjust the power distribution ratio according to the changing path loss situation. Then, the master base station determines whether to apply the updated power distribution ratio, that is, the updated value of the maximum output power of the mobile station for uplink transmission to the master base station and the secondary base station (P _{EMAX , MeNB} ) / (P _{EMAX, SeNB} ) can be determined according to any of the several alternative methods described above to determine whether to reset the power distribution ratio. In any alternative method, the secondary base station and the mobile station receive the updated value and adopt that value, so that the secondary base station is up according to these new updated values of maximum output power. With link scheduling, the mobile station can perform uplink transmission.

  Up to this point, for the step in which the master base station updates the power distribution ratio, the master base station is mainly configured by providing the master base station with information on changes in path loss and information on (changes) in the path loss. It has been explained in relation to how to support.

  According to the second aspect of the present disclosure, in other cases, for example, the case where the uplink radio link is not used (eg over a certain minimum time length) or the case where the (uplink) radio link is unavailable Extend the mobile station with additional functionality to assist the master base station with respect to the step of updating power distribution. In any case, it is advantageous if the power distribution is updated so that the power allocated to a radio link that is not used or not available on the uplink is used by the other radio link. This will be described in detail below.

  The main idea is that the mobile station determines when the radio link (first radio link or second radio link) becomes inactive or unavailable (ie radio link failure) and Let the base station know. Thus, updating the power distribution ratio so that all of the power available at the mobile station is allocated for uplink transmissions to other base stations (through available or active uplink radio links) Can do.

More specifically, the mobile station determines when the first radio link becomes inactive. That is, the mobile station predicts that it will not transmit data on the uplink to the master base station for a specific time. An example of such a case is a case where the mobile station enters a discontinuous reception / transmission mode (DRX / DTX) in its first radio link. In this case, the secondary base station is informed that the first radio link becomes inactive. Thereby, the secondary base station can determine the updated value (P _{EMAX, SeNB} ) of the maximum output power of the mobile station for uplink transmission to the secondary base station. This updated value is specifically the total maximum output power (because no power is required for uplink transmission on the other radio link that is inactive). This updated value is then transmitted to the mobile station, and the mobile station adopts the updated value of the maximum output power when uplink transmitting to the secondary base station.

Similarly, the mobile station determines when the second radio link becomes inactive. That is, the mobile station predicts that data will not be transmitted on the uplink to the secondary base station for a specific time. An example of such a case is a case where the mobile station enters a discontinuous reception / transmission mode (DRX / DTX) in the second radio link. In this particular case, it informs the master base station that the second radio link will become inactive, so that the master base station can control the maximum output power of the mobile station for uplink transmission to the master base station. An updated value (P _{EMAX, MeNB} ) can be determined, which is specifically the total maximum output power (for uplink transmission on the other radio link that is inactive) Because no power is needed). This updated value can then be transmitted to the mobile station, so that the mobile station adopts the updated value of maximum output power when uplink transmitting to the master base station.

  As described above, there are several options for informing the master base station and the secondary base station that the second radio link and the first radio link will become inactive, respectively. Several are disclosed.

  When the mobile station recognizes that the second radio link will become inactive on the uplink, it may generate a first power headroom report for the first radio link between the mobile station and the master base station. And a predetermined flag in this first power headroom report can be set to inform the master base station that the second radio link is inactive in the uplink, and then The first power headroom report created in can be sent to the master base station. Alternatively, the mobile station can create a secondary virtual power headroom report for the second radio link between the mobile station and the secondary base station, and the predetermined number in the secondary virtual power headroom report The flag can be set to inform the master base station that the second radio link will become inactive on the uplink, and then send the secondary virtual power headroom report thus created to the master base station be able to. According to yet another alternative, the mobile station can generate a secondary virtual power headroom report for the second radio link, which means that the second radio link becomes inactive on the uplink. A predetermined power headroom value (e.g., a negative value) recognized by the master base station as to be included in this secondary virtual power headroom report. Next, the secondary virtual power headroom report created in this way is sent from the mobile station to the master base station.

  Conversely, when the mobile station recognizes that the first radio link between the mobile station and the master base station is inactive in the uplink, the mobile station may use the second power head of the second radio link. A room report can be generated and a predetermined flag in this second power headroom report is set to inform the secondary base station that the first radio link is inactive in the uplink The second power headroom report thus created can then be sent to the secondary base station. Alternatively, the mobile station can create a secondary virtual power headroom report for the second radio link, and the first radio link ups a predetermined flag in the secondary virtual power headroom report. The secondary base station can be configured to inform the secondary base station that it will become inactive on the link, and the secondary virtual power headroom report thus created can then be sent to the secondary base station. According to yet another alternative, the mobile station can create a secondary virtual power headroom report for the second radio link, which means that the first radio link becomes inactive on the uplink. A predetermined power headroom value (e.g., a negative value) recognized by the secondary base station as being included is included in this secondary virtual power headroom report. Next, the secondary virtual power headroom report created in this way is sent from the mobile station to the secondary base station.

  According to a further refinement of the above method for reporting that the first radio link / second radio link becomes inactive, the mobile station may be configured such that the first radio link / second radio link is not in the uplink. The length of time expected to be active can be determined / estimated, and only when the determined time length exceeds a predetermined time length (eg, 100 ms or 200 ms), the corresponding base station (secondary base station / Inform the master base station of this situation. This mechanism for resetting power distribution is advantageous because it is efficient and is not performed when the time of inactivity is very short.

  In yet another refinement of the second aspect described above, the base station (corresponding base station of the master base station or secondary base station) does not need to be informed again by the mobile station after a certain time, Return the power distribution to the previous state (ie, the power distribution ratio before the update). More specifically, as explained above, the mobile station informs the master base station / secondary base station when the second radio link / first radio link becomes inactive, thereby The master base station / secondary base station updates the power distribution and provides the mobile station with an updated value of the maximum output power used for uplink transmission to the master base station / secondary base station. Set a power control timer so that the mobile station does not need to inform the master / secondary base station again when the second radio link / first radio link becomes active again It is possible. When this power control timer expires, it triggers the master base station / secondary base station to return to the power distribution ratio before the update. The value of the power control timer can be a predetermined value or set in advance. Or, according to a further refinement, the value of the power control timer is determined by the mobile station in each case (perhaps the mobile station is most accurately able to recognize when the radio link inactivity time is expected to end) I can inform you. The notification method can be, for example, by transmitting the corresponding value of the power control timer directly to the master base station / secondary base station or, preferably, the second radio link / first radio link becomes inactive To the (eg negative) power headroom value in the secondary virtual power headroom report sent from the mobile station to the master base station / secondary base station to inform the master base station / secondary base station (see description above) ), By encoding the value of the power control timer.

  The power control timer described above is started by the master base station / secondary base station when determining and transmitting the updated maximum output power of the mobile station for uplink transmission to the master base station / secondary base station. Is preferred and operates over a specific period of time (see description above).

  Similarly, a situation in which the mobile station recognizes that the first radio link / second radio link enters the radio link failure state (that is, becomes unavailable) will be described below as the situation described above.

  When the mobile station recognizes that the second radio link from the mobile station to the secondary base station enters the radio link failure state, it informs the master base station through the available radio link. This step can be performed, for example, according to any of the following methods.

  Upon recognizing the radio link failure of the second radio link to the secondary base station, the mobile station creates a first power headroom report for the first radio link between the mobile station and the master base station, and this The corresponding predetermined flag in the first power headroom report is set to inform the master base station of the radio link failure of the second radio link, and then the first radio link thus created The first power headroom report can be sent to the master base station. Alternatively, the mobile station can create a secondary virtual power headroom report for the second radio link between the mobile station and the secondary base station, and the predetermined number in the secondary virtual power headroom report The flag can be set to notify the master base station of the radio link failure of the second radio link, and the secondary virtual power headroom report thus created can then be sent to the master base station. According to yet another alternative, the mobile station can generate a secondary virtual power headroom report for the second radio link between the mobile station and the secondary base station, where the second radio link A predetermined virtual power headroom value recognized by the master base station as indicating a radio link failure is included in the secondary virtual power headroom report. Next, the secondary virtual power headroom report created in this way is sent from the mobile station to the master base station.

The master base station, after receiving the information about the failure of the second radio link, determines the updated value (P _{EMAX, MeNB} ) of the maximum output power of the mobile station for uplink transmission to the master base station Can do. The master base station then transmits this updated parameter to the mobile station. For example, the master base station can determine that the mobile station can use all of its maximum output power for uplink transmissions to the master base station. This is because uplink transmission to the secondary base station cannot be performed due to the failure of the second radio link. According to a preferred solution, the master base station further initiates an appropriate procedure for resolving the radio link failure of the second radio link.

  Conversely, when the mobile station recognizes a radio link failure of the first radio link to the master base station, the mobile station creates a second power headroom report for the second radio link, and this second The corresponding predetermined flag in the power headroom report is set to inform the secondary base station of the radio link failure of the first radio link, and then the mobile station creates the second power head thus created Send room report to secondary base station. Instead, the mobile station creates a secondary virtual power headroom report for the second radio link and sets the corresponding predetermined flag in the secondary virtual power headroom report to the radio link for the first radio link. The failure is set to notify the secondary base station, and the secondary virtual power headroom report thus created is then sent to the secondary base station. According to yet another alternative, the mobile station creates a secondary virtual power headroom report for the second radio link, which is then recognized by the master base station as indicating a radio link failure for the first radio link. The predetermined virtual power headroom value is included in this secondary virtual power headroom report. Next, the secondary virtual power headroom report created in this way is sent from the mobile station to the secondary base station.

The secondary base station, after receiving the information on the failure of the first radio link, determines an updated value (P _{EMAX, SeNB} ) of the maximum output power of the mobile station for uplink transmission to the secondary base station Can do. Next, the secondary base station transmits this updated parameter to the mobile station. For example, the secondary base station can determine that the mobile station can use all of its maximum output power for uplink transmission to the secondary base station. This is because uplink transmission to the master base station cannot be performed due to the failure of the first radio link. According to a preferred solution, the secondary base station further initiates an appropriate procedure for resolving the radio link failure of the first radio link.

  One embodiment of the present disclosure provides a method for power headroom reporting in a mobile communication system. The mobile station is connected to the master base station via a first radio link, and is connected to at least one secondary base station via a second radio link. The mobile station calculates a first power headroom report for the first radio link between the mobile station and the master base station. The mobile station calculates the calculated first power headroom report, along with information that allows the master base station to determine information about the path loss of the second radio link between the mobile station and the secondary base station, Transmit to the master base station. Further, the mobile station calculates a second power headroom report for the second radio link between the mobile station and the secondary base station, and sends the calculated second power headroom report from the mobile station to the secondary base station. Send to.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the information based on when the master base station determines information about the path loss is the mobile station And the secondary virtual power headroom report of the second radio link between the secondary base station and the secondary base station. In this case, the mobile station determines the second radio link between the mobile station and the secondary base station based on the virtual uplink resource allocation set in advance for the second radio link to the secondary base station. Calculate the secondary virtual power headroom report. According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the master base station can be used between a master base station and a secondary base station, Determine an initial distribution of the maximum transmit power available to the mobile station. This step includes the maximum output power of the mobile station for uplink transmission to the master base station (P _{EMAX, MeNB} ) and the maximum output power of the mobile station for uplink transmission to the secondary base station (P _{EMAX, SeNB} ). And determining. The determined maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station is preferably a signaling message transmitted via the interface between the master base station and the secondary base station In FIG. 2, the data is transmitted from the master base station to the secondary base station. Next, the determined maximum output power of the mobile station for uplink transmission to the master base station (P _{EMAX, MeNB} ) and the determined maximum output power of the mobile station for uplink transmission to the secondary base station (P _{Both EMAX, SeNB} ) are preferably transmitted from the master base station to the mobile station in a radio resource control (RRC) message or in a media access control (MAC) control element. Alternatively, the determined maximum output power (P _{EMAX, MeNB} ) of the mobile station for uplink transmission to the master base station is preferably in a radio resource control (RRC) message or a media access control (MAC) control element , The maximum output power (P _{EMAX, SeNB} ) determined by the mobile station for uplink transmission to the secondary base station is transmitted from the master base station to the mobile station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the master base station can be used between a master base station and a secondary base station, Determine an initial distribution of the maximum transmit power available to the mobile station. This step includes the maximum output power of the mobile station for uplink transmission to the master base station (P _{EMAX, MeNB} ) and the maximum output power of the mobile station for uplink transmission to the secondary base station (P _{EMAX, SeNB} ). And determining. Next, the determined maximum output power of the mobile station for uplink transmission to the master base station (P _{EMAX, MeNB} ) and the determined maximum output power of the mobile station for uplink transmission to the secondary base station (P _{EMAX, SeNB} ) are preferably transmitted from the master base station to the mobile station in a radio resource control (RRC) message or in a media access control (MAC) control element. Further, the mobile station transmits information regarding the received maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station to the secondary base station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the maximum received power of the mobile station for uplink transmission to the secondary base station The step of transmitting information on the power (P _{EMAX, SeNB} ) by the mobile station to the secondary base station is the following steps: up from the mobile station to the secondary base station for inclusion in the secondary virtual power headroom report The cell-specific maximum output power (P _{CMAX, SeNB} ) set by the mobile station for link transmission, and the received maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station ) And a secondary base station determines whether the mobile station for uplink transmission to the secondary base station Large output power (P _{EMAX, SeNB)} to be able to determine, is set by the mobile station from the mobile station for uplink transmission to the secondary base station, the maximum output power was determined specific to the cell (P _{CMAX , SeNB} ) from the mobile station to the secondary base station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the maximum received power of the mobile station for uplink transmission to the secondary base station The step of transmitting information related to power (P _{EMAX, SeNB} ) to the secondary base station by the mobile station includes the following steps, ie, virtual upset in advance for the second radio link to the secondary base station Calculating a secondary virtual power headroom report for a second radio link between the mobile station and the secondary base station by the mobile station based on the link resource allocation, the mobile station to the secondary base station The maximum output power ( _{PCMAX, SeNB} ) specific to the cell set by the mobile station for link transmission is set to the secondary base. A step of determining based on the received maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the station, the secondary base station of the mobile station for uplink transmission to the secondary base station A cell configured by the mobile station for uplink transmission from the mobile station to the secondary base station, and the calculated secondary virtual power headroom report so that the maximum output power (P _{EMAX, SeNB} ) can be determined _{Transmitting the} determined maximum output power ( _{PCMAX, SeNB} ) unique to the mobile station to the secondary base station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the master base station is a second between the mobile station and the secondary base station. Based on the determined information regarding the path loss of the radio link, an updated distribution of the maximum transmission power available to the mobile station between the master base station and the secondary base station is determined. This step includes the update of the maximum output power of the mobile station for uplink transmission to the master base station (P _{EMAX, MeNB} ) and the maximum output power of the mobile station for uplink transmission to the secondary base station. Determining an updated value (P _{EMAX, SeNB} ). The updated maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station is transmitted from the master base station to the secondary base station. Then, the updated maximum output power of the mobile station for uplink transmission to the master base station (P _{EMAX, MeNB} ) and the updated maximum output power of the mobile station for uplink transmission to the secondary base station (P _{Both EMAX, SeNB} ) are transmitted from the master base station to the mobile station, or the updated maximum output power (P _{EMAX, MeNB} ) of the mobile station for uplink transmission to the master base station is The updated maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station is transmitted from the station to the mobile station, and transmitted from the secondary base station to the mobile station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the first power headroom report of the calculated first radio link is Extended power headroom report, which is a cell-specific maximum output power (P _{CMAX, MeNB} ) set by the mobile station for uplink transmission from the mobile station to the master base station. In addition, the second power link second power report for the second radio link that is calculated is an extended power headroom report, and the extended power headroom report is moved for uplink transmission from the mobile station to the secondary base station. Further included is a cell-specific maximum output power (P _{CMAX, SeNB} ) set by the station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the second radio link between the mobile station and the secondary base station according to an advantageous variant of the disclosed embodiment When the mobile station recognizes that it will become inactive on the uplink, the mobile station provides information to the master base station regarding the second radio link becoming inactive on the uplink. In a preferred solution, the information about the second radio link becoming inactive in the uplink is in the following form:
A bit flag having a predetermined value in the first power headroom report of the first radio link between the mobile station and the master base station, or
A bit flag having a predetermined value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station, or
The predetermined power headroom value of the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station;
In the form of a master base station.

  According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the mobile station may have the second radio link inactive in the uplink The mobile station provides information to the master base station about the second radio link becoming inactive only if the expected time length is determined and the determined time length exceeds a predetermined time length. To do.

  According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the information regarding the second radio link becoming inactive in the uplink is: Provided to the master base station in the form of a predetermined power headroom value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station. The predetermined power headroom value is preferably a predetermined negative value that encodes time information related to a length of time predicted by the mobile station that the second radio link is inactive in the uplink.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the master base station makes the second radio link inactive in the uplink Determining an updated distribution of the maximum available transmit power of the mobile station between the master base station and the secondary base station based on the received information about the, this step at least to the master base station Determining an updated value (P _{EMAX, MeNB} ) of the maximum output power of the mobile station for uplink transmission. The master base station transmits the updated maximum output power (P _{EMAX, MeNB} ) of the mobile station for uplink transmission to the master base station to the mobile station.

According to an advantageous variant of the embodiment of the present disclosure, which can be used in addition to or in place of the above embodiment, the master base station can be configured for a mobile station for uplink transmission to the master base station. When the updated maximum output power (P _{EMAX, MeNB} ) is determined and transmitted, the power control timer is started. When the power control timer expires, the master base station transmits the maximum output power (P _{EMAX, MeNB} ) of the mobile station for uplink transmission to the master base station before the update to the mobile station. The power control timer
-A predetermined time value, or
The information about the second radio link becoming inactive in the uplink is in the form of a predetermined power headroom value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station; Provided to the master base station, and the predetermined power headroom value is preferably a predetermined negative encoding encoding time information relating to a length of time during which the second radio link is expected to be inactive in the uplink. Value, the time value indicated by the mobile station in the received secondary virtual power headroom report including a predetermined negative power headroom value,
Is preferably set using.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the first radio link between the mobile station and the master base station according to an advantageous variant of the embodiment of the present disclosure When the mobile station recognizes that it will become inactive on the uplink, the mobile station provides information to the secondary base station about the first radio link becoming inactive on the uplink. Information about the first radio link becoming inactive in the uplink has the following form:
A bit flag having a predetermined value in the second power headroom report of the second radio link between the mobile station and the secondary base station, or
A bit flag having a predetermined value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station, or
The predetermined power headroom value of the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station;
In the form of a secondary base station.

  According to an advantageous variant of the embodiment of the present disclosure, which can be used in addition to or in place of the above embodiment, the mobile station has the first radio link inactive in the uplink The mobile station provides information to the secondary base station about the first radio link becoming inactive only if the expected time length is determined and the determined time length exceeds a predetermined time length. To do.

  According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the information regarding the first radio link becoming inactive in the uplink is: Provided to the secondary base station in the form of a predetermined power headroom value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station. In this case, the predetermined power headroom value is preferably a predetermined negative value that encodes time information regarding the length of time predicted by the mobile station that the first radio link is inactive in the uplink. is there.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the secondary base station can An updated value (P _{EMAX, SeNB} ) of the maximum output power is determined. The secondary base station transmits the updated maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station to the mobile station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the secondary base station can be configured for a mobile station for uplink transmission to the secondary base station. When the updated maximum output power (P _{EMAX, SeNB} ) is determined and transmitted, the power control timer is started. When the power control timer expires, the secondary base station transmits the maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station before the update to the mobile station. The power control timer
-A predetermined time value, or
The information about the first radio link becoming inactive in the uplink is in the form of a predetermined power headroom value of the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station; Provided to the secondary base station. The predetermined power headroom value is preferably a predetermined negative value that encodes time information regarding the length of time predicted by the mobile station that the first radio link is inactive in the uplink, A time value indicated by the mobile station in the received secondary virtual power headroom report including a predetermined negative power headroom value,
Is preferably set using.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the second radio link from the mobile station to the secondary base station is in a radio link failure state Upon entering, the mobile station provides information about the radio link failure of the second radio link, preferably in the following form:
A bit flag having a predetermined value in the first power headroom report of the first radio link between the mobile station and the master base station, or
A bit flag having a predetermined value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station, or
The predetermined power headroom value of the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station;
In the form of a master base station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the master base station has received a radio link failure of the second radio link. Based on the information, an updated distribution of the maximum transmit power available for the mobile station between the master base station and the secondary base station is determined. This step includes at least determining an updated value (P _{EMAX, MeNB} ) of the maximum output power of the mobile station for uplink transmission to the master base station. The master base station transmits the updated value (P _{EMAX, MeNB} ) of the maximum output power of the mobile station for uplink transmission to the master base station to the mobile station. The master base station preferably initiates an appropriate procedure for resolving the radio link failure of the second radio link.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the first radio link from the mobile station to the master base station is in a radio link failure state Upon entering, the mobile station provides information about the radio link failure of the first radio link, preferably in the following form:
A bit flag having a predetermined value in the second power headroom report of the second radio link between the mobile station and the secondary base station, or
A bit flag having a predetermined value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station, or
The predetermined power headroom value of the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station;
In the form of a secondary base station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the secondary base station can An updated value (P _{EMAX, SeNB} ) of the maximum output power is determined. The secondary base station transmits the updated maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station to the mobile station. The secondary base station preferably initiates an appropriate procedure for resolving the radio link failure of the first radio link.

  This first embodiment of the present disclosure is a mobile station reporting power headroom in a mobile communication system, connectable to a master base station via a first radio link, and a second radio There is further provided a mobile station, connectable to at least one secondary base station via a link. The mobile station's processor calculates a first power headroom report for the first radio link between the mobile station and the master base station. The mobile station transmitter allows the master base station to determine the calculated first power headroom report and information about the path loss of the second radio link between the mobile station and the secondary base station. Together with the information to be transmitted to the master base station. The processor further calculates a second power headroom report for the second radio link between the mobile station and the secondary base station. The transmitter then transmits the calculated second power headroom report to the secondary base station.

  According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the information based on when the master base station determines information about the path loss is the mobile station And the secondary virtual power headroom report of the second radio link between the secondary base station and the secondary base station. In this case, the processor uses the second uplink of the second radio link between the mobile station and the secondary base station based on the virtual uplink resource allocation set in advance for the second radio link to the secondary base station. A virtual power headroom report is calculated.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the receiver of the mobile station is for uplink transmission to a secondary base station. The maximum output power of the mobile station (P _{EMAX, SeNB} ) or the maximum output power of the mobile station for uplink transmission to the master base station (P _{EMAX, MeNB} ), or both, preferably, radio resource control ( Received from the master base station in an RRC) message or at a media access control (MAC) control element.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the receiver of the mobile station is for uplink transmission to a secondary base station. The mobile station receives the maximum output power (P _{EMAX, SeNB} ) of the mobile station, and the transmitter receives information on the received maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station. Send to base station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the processor receives the mobile station for uplink transmission to the secondary base station. Cell-specific maximum configured by the mobile station for uplink transmission from the mobile station to the secondary base station for inclusion in the secondary virtual power headroom report based on the maximum output power (P _{EMAX, SeNB} ) The output power ( _{PCMAX, SeNB} ) is determined. The transmitter _uplinks from the mobile station to the secondary base station so that the secondary base station can determine the maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station. The determined maximum output power ( _{PCMAX, SeNB} ) specific to the cell set by the mobile station for transmission is transmitted to the secondary base station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the processor is pre-provisioned for the second radio link to the secondary base station. Calculate a secondary virtual power headroom report for the second radio link between the mobile station and the secondary base station based on the configured virtual uplink resource allocation. This step is performed by the mobile station for uplink transmission from the mobile station to the secondary base station, based on the received maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station. Determining a cell-specific maximum output power (P _{CMAX, SeNB} ) to be set. The transmitter is configured to calculate a secondary virtual power headroom report so that the secondary base station can determine the maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station; The determined maximum output power ( _{PCMAX, SeNB} ) specific to the cell, which is set by the mobile station for uplink transmission from the mobile station to the secondary base station, is transmitted to the secondary base station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the processor can provide a second radio link between the mobile station and the secondary base station. When recognizing that it will become inactive on the uplink, the transmitter will provide information regarding that the second radio link will become inactive on the uplink, preferably in the following form:
A bit flag having a predetermined value in the first power headroom report of the first radio link between the mobile station and the master base station, or
A bit flag having a predetermined value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station, or
The predetermined power headroom value of the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station;
In the form of a master base station.

  According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the processor may determine that the second radio link is inactive in the uplink. Determine the expected time length and only if the determined time length exceeds the predetermined time length, the transmitter provides information to the master base station that the second radio link is inactive in the uplink .

  According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the information regarding the second radio link becoming inactive in the uplink is: Provided to the master base station in the form of a predetermined power headroom value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station. In this case, the processor encodes a predetermined power headroom value, preferably a predetermined negative value that encodes time information relating to a length of time predicted by the mobile station that the second radio link is inactive in the uplink. Set to the value of.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the processor has a first radio link between the mobile station and the master base station. Upon recognizing that it will become inactive on the uplink, the transmitter will provide information regarding that the first radio link will become inactive on the uplink, preferably in the following form:
A bit flag having a predetermined value in the second power headroom report of the second radio link between the mobile station and the secondary base station, or
A bit flag having a predetermined value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station, or
The predetermined power headroom value of the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station;
In the form of a secondary base station.

  According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the processor may determine that the first radio link is inactive in the uplink. Determine the expected time length and only if the determined time length exceeds a predetermined time length, the transmitter provides information to the secondary base station that the first radio link is inactive in the uplink .

  According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the information regarding the first radio link becoming inactive in the uplink is: Provided to the secondary base station in the form of a predetermined power headroom value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station. In this case, the processor encodes a predetermined power headroom value, preferably a predetermined negative value that encodes time information relating to a length of time predicted by the mobile station that the first radio link is inactive in the uplink. Set to the value of.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the processor has a second radio link between the mobile station and the secondary base station. When recognizing that it enters a radio link failure, the transmitter can provide information regarding the failure of the second radio link, preferably in the following form:
A bit flag having a predetermined value in the first power headroom report of the first radio link between the mobile station and the master base station, or
A bit flag having a predetermined value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station, or
The predetermined power headroom value of the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station;
In the form of a master base station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the processor has a first radio link between the mobile station and the master base station. When recognizing that it enters a radio link failure, the transmitter preferably provides information regarding the failure of the first radio link in the following form:
A bit flag having a predetermined value in the second power headroom report of the second radio link between the mobile station and the secondary base station, or
A bit flag having a predetermined value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station, or
The predetermined power headroom value of the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station;
In the form of a secondary base station.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the receiver is a mobile station maximum for uplink transmission to a secondary base station. The updated value (P _{EMAX, MeNB} ) of the mobile station for uplink transmission to the master base station and the updated value (P _{EMAX, MeNB} ) are received.

  This first embodiment of the present disclosure further provides a master base station that receives a power headroom report from a mobile station in a mobile communication system. The mobile station is connected to the master base station via a first radio link, and is connected to at least one secondary base station via a second radio link. The master base station receiver allows the master base station to determine a first power headroom report and information about the path loss of the second radio link between the mobile station and the secondary base station. Received from the mobile station along with the information. The processor of the master base station determines information on the path loss of the second radio link between the mobile station and the secondary base station based on the received information.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the processor moves between the master base station and the secondary base station. Determine the initial distribution of the maximum transmit power available to the station. This step includes the maximum output power of the mobile station for uplink transmission to the master base station (P _{EMAX, MeNB} ) and the maximum output power of the mobile station for uplink transmission to the secondary base station (P _{EMAX, SeNB} ). And determining. The transmitter of the master base station transmits the determined maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station, preferably between the master base station and the secondary base station. In a signaling message transmitted via the interface, the secondary base station transmits the message. The transmitter determines the maximum output power (P _{EMAX, MeNB} ) of the mobile station for uplink transmission to the master base station, or the determined maximum of the mobile station for uplink transmission to the secondary base station The output power (P _{EMAX, SeNB} ), or both, is transmitted to the mobile station, preferably in a radio resource control (RRC) message or in a media access control (MAC) control element.

According to an advantageous variant of the embodiment of the present disclosure that can be used in addition to or in place of the above embodiment, the processor is a mobile station between the master base station and the secondary base station. Is determined based on the determined information regarding the path loss of the second radio link between the mobile station and the secondary base station. This step includes the updated value (P _{EMAX, MeNB} ) of the maximum output power of the mobile station for uplink transmission to the master base station and the maximum output power of the mobile station for uplink transmission to the secondary base station. Determining an updated value of (P _{EMAX, SeNB} ). The transmitter of the master base station transmits the updated maximum output power (P _{EMAX, SeNB} ) of the mobile station for uplink transmission to the secondary base station to the secondary base station. The transmitter can update the maximum output power (P _{EMAX, MeNB} ) of the mobile station for uplink transmission to the master base station, or the updated maximum of the mobile station for uplink transmission to the secondary base station. Output power (P _{EMAX, SeNB} ) or both are transmitted to the mobile station.

  A “mobile station” or “mobile node” is a physical entity within a communication network. A node can have several functional entities. A functional entity means a software module or hardware module that performs a predetermined set of functions and / or provides a predetermined set of functions to another functional entity of a node or network. A node can have one or more interfaces that attach the node to a communication device or communication medium, and the nodes can communicate through these interfaces. Similarly, a network entity can have a logical interface that attaches the functional entity to a communication device or communication medium, and the network entity can communicate with another functional entity or correspondent node through the logical interface.

  The term “master base station” as used throughout the claims and throughout the present disclosure should be construed as used in the field of 3GPP LTE-A dual connectivity. Therefore, as another terminology, a macro base station, a master eNB, a macro eNB, a serving base station, or some other term determined in the future by 3GPP is conceivable. Similarly, the term “secondary base station” used throughout the claims and the description should be interpreted as meaning used in the field of dual connectivity of 3GPP LTE-A. Therefore, as another term, a slave base station, a secondary eNB, a slave eNB, or some other term determined in the future by 3GPP is conceivable.

  The term “radio link” as used throughout the claims and throughout the present disclosure should be broadly understood as a wireless connection between a mobile station and a base station.

  The term “power headroom report” shall mean a power headroom report as defined in 3GPP, and preferably an extended power headroom report as defined in 3GPP, in certain embodiments of the disclosure. Shall mean.

  The term “virtual power headroom report” shall refer to a virtual power headroom report as defined in 3GPP in certain embodiments of the present disclosure.

  In the following, some embodiments of the present disclosure will be described in detail. For illustrative purposes only, most of these embodiments are based on the 3GPP LTE (Release 8/9) and LTE-A (Release 10/11) mobile communication systems (part of the background art above). Explained in the section). It should be noted that the present disclosure can also be used advantageously in mobile communication systems such as, for example, the 3GPP LTE-A (Release 12) communication system described in the Background section above. The embodiments described in detail below are examples used in connection with functionality defined in 3GPP LTE and / or 3GPP LTE-A, or examples of enhancing such functionality, or It is described as an example that is both. In this regard, 3GPP LTE and / or 3GPP LTE-A terminology is employed throughout the description. Additionally, exemplary system configurations are discussed to detail the overall concept / principle of the present disclosure.

  The following description should not be construed as limiting the present disclosure, but merely as examples of embodiments for a thorough understanding of the present disclosure. Those skilled in the art will recognize that the general principles of the present disclosure as set forth in the claims can be applied to various scenarios in a manner not explicitly described herein. . Accordingly, the following scenarios envisioned for purposes of describing various embodiments do not limit the present disclosure thereto.

  Various examples are described in connection with the present disclosure. Several assumptions are made to simplify the explanation of the principles of the present disclosure. However, these assumptions are not to be construed as limiting the scope of the present disclosure as broadly defined by the claims.

  The present disclosure will be described with reference to FIGS. Assuming a dual connectivity scenario in a small cell environment, in this case, the UE is connected to both the master base station (MeNB) and the secondary base station (SeNB) via the first radio link and the second radio link, respectively. It is connected. However, it should be noted that the present disclosure is not limited to this scenario. For example, a scenario is possible in which the UE is connected to one master base station and at least two secondary base stations.

  According to the present disclosure, one of the master base station and the secondary base station controls the power distribution of the UE between the uplink transmission to the master base station and the uplink transmission to the secondary base station. Take on. In the following description of the present disclosure, it is assumed that the master base station plays the role of controlling power distribution. However, the principles of the present disclosure are equally applicable (with the necessary changes) to scenarios where a secondary base station is selected as a base station responsible for controlling power distribution.

According to the power control already defined by 3GPP (see background section), the UE typically sets the maximum output power allowed to be used for uplink transmission by the base station (eNB). To be determined and signaled based on its own power class and maximum power cap (ie, P _EMAX ). The P _EMAX is determined by the (master) base station and transmitted to the UE. The UE may lower its maximum transmit power, possibly applying additional power limitations such as MPR or A-MPR so that it can meet the requirements for signal quality, spectral emission mask, and spurious emission.

When a UE (connected to a master base station) enters a dual connectivity state, i.e., when a cell controlled by a secondary base station is configured and added, according to the present disclosure, the UEs available for uplink transmission It is advantageous to determine the initial power distribution between the master base station and the secondary base station (ie determine two parameters P _{EMAX, MeNB} and P _{EMAX, SeNB} ). P _{EMAX, MeNB} shall be understood as the maximum output power that the mobile station uses for uplink transmission to the master base station. Similarly, P _{EMAX, SeNB} shall be understood as the maximum output power that the mobile station uses for uplink transmission to the secondary base station. More generally, the master base station allows mobile stations to transmit on each uplink component carrier (or cell) belonging to the same base station or different base stations, or a set of configured uplink component carriers. The maximum power that can be done can be determined. If one base station (master base station or secondary base station) is controlling further component carriers, that base station will use the signaled maximum allowed uplink transmission power (P _{EMAX, MeNB} and P _{EMAX, SeNB} ). Can be further distributed among the component carriers.

The master base station considers one or more of the following parameters in order to determine the initial ratio of efficient and appropriate power distribution (ie the two parameters P _{EMAX, MeNB} and P _{EMAX, SeNB} ) Can do.
-Path loss on the two radio links between the UE and the master / secondary base station. This path loss is one indicator of how far the UE is from the master base station or secondary base station (distance from the UE to the master base station or secondary base station). Thus, the path loss allows the UE to determine the power required to transmit data to the master base station and the secondary base station and the optimal power distribution ratio.
-Information about the traffic load handled by the master base station and the secondary base station-uplink resources available for the two radio links

As a result, how the master base station distributes the maximum allowable uplink transmission power between uplink transmission from the UE to the master base station and uplink transmission from the UE to the secondary base station (Ie, the master base station determines the values of P _{EMAX, MeNB} and P _{EMAX, SeNB} ). For example, when a mobile terminal having a maximum transmission power of 23 dBm communicates with a master base station and a secondary base station, the master base station can set the maximum allowable uplink transmission power to 20 dBm for each base station. As another example, the power distribution ratio is set to 1: 2, that is, P _{EMAX, MeNB} = P _CMAX / 3, P _{EMAX, SeNB} = 2 * P _CMAX / 3. It should be understood that _PCMAX generally refers to the maximum uplink transmission power available to the UE. Since the master base station does not accurately recognize the _PCMAX set by the mobile station, it makes some prediction of this value, or the worst case (the maximum power reduction allowed by the specification (ie MPR)) _Either (which the mobile station applies) is always assumed (equivalent to assuming P _{CMAX_L} as P _CMAX ).

_After the initial values of P _{EMAX, MeNB} and P _{EMAX, SeNB} are determined by the master base station, these parameters are distributed to the secondary base station and UE so that the secondary base station and UE can use them in their respective power control procedures. Is done. Specifically, the UE needs both P _{EMAX, MeNB} and P _{EMAX, SeNB} in order to properly control the output power for uplink transmission to both the master base station and the secondary base station. However, the secondary base station only needs the parameters P _{EMAX, SeNB} .

FIGS. 17-19 _show different embodiments for how to properly distribute these parameters from the master base station so that the two parameters P _{EMAX, MeNB} and P _{EMAX, SeNB} are received by the secondary base station and the UE. Show. According to the first alternative embodiment shown in FIG. 17, the master base station can transmit P _{EMAX, MeNB} and P _{EMAX, SeNB} to the UE, and can transmit P _{EMAX, SeNB} to the secondary base station. Further, in this particular scenario of FIG. 17, the parameters P _{EMAX, MeNB} and P _{EMAX, SeNB} are transmitted via RRC signaling (ie as RRC configuration). Alternatively, although not shown in FIG. 17, two parameters P _{EMAX, MeNB} and P _{EMAX, SeNB} may be transmitted from the master base station to the UE as MAC control elements. Furthermore, the parameters P _{EMAX and SeNB} are preferably transmitted from the master base station to the secondary base station via the Xn interface.

According to another alternative embodiment, as shown in FIG. 18, the parameters P _{EMAX, SeNB} are transmitted from the master base station to the secondary base station in the same way as in FIG. 17 (ie preferably via the Xn interface). To do. However, it is not the master base station but the secondary base station that transmits the parameters P _{EMAX, SeNB} to the UE. This transmission can be performed by using a MAC control element as shown in FIG. The master base station _transmits the parameters P _{EMAX, MeNB} to _{the UE} , for example as part of the RRC configuration or in the MAC control element (not shown in FIG. 18).

According to yet another embodiment, as shown in FIG. 19, the master base station transmits P _{EMAX, MeNB} and P _{EMAX, SeNB} to the UE. In this case, unlike the embodiments of FIGS. 17 and 18, the master base station does not need to transmit P _{EMAX, SeNB} to the secondary base station because this transmission is performed by the UE as follows. The UE can transmit P _{EMAX, SeNB} to the secondary base station in several ways. As a simple method, although not shown in FIG. 19, after receiving _{the PEMAX} and _SeNB from the master base station, the UE directly transfers this parameter to the secondary base station, for example, within a specific MAC control element. To do. Instead, the UE can calculate virtual P _{CMAX, SeNB} (maximum power used for calculation of virtual power headroom) that is a power-related parameter based on the received P _{EMAX, SeNB} . Basically, according to the virtual power headroom _{report, P CMAX, SeNB} is _{P CMAX_H,} equal to _{c, P CMAX_H, c} is _{P EMAX,} equal to _SeNB. Accordingly, the UE can transmit virtual _{PCMAX and SeNB} to the secondary base station as shown in FIG. According to another embodiment, the UE further calculates the virtual power headroom report (V-PHR _SeNB ) of the secondary link after calculating the virtual _{PCMAX, SeNB} as described above, Send to base station. FIG. 20 shows one method of transmitting these two parameters V-PHR _SeNB and virtual _{PCMAX, SeNB} together to the secondary base station. This figure shows the structure of the MAC control element of the power headroom report, which is the extended power headroom report (lines 2-5, for the second radio link to the secondary base station). In the background section, see also the corresponding description for Type 2 / Type 1 extended PHR including additional _{PCMAX, c,} etc.), and also the virtual power headroom value and the corresponding _{PCMAX, SeNB} (usually Is not transmitted with the virtual PHR).

As illustratively described above in connection with FIGS. 17-19, secondary base stations and UEs are provided with the necessary parameters P _{EMAX, MeNB} and P _{EMAX, SeNB and} are therefore already standardized by 3GPP. These parameters can be applied to normal power control procedures. That is, the UE calculates its own P _{CMAX, MeNB} and P _{CMAX, SeNB} to be used for uplink transmission scheduled by the master base station and the secondary base station (applying further power reduction if necessary).

Thus, the parameters P _{EMAX, SeNB} and P _{EMAX, MeNB} can be delivered from the master base station to the secondary base station and UE by one of the various alternative methods described above. These same alternatives can also be used in further refinements that subsequently _deliver updated values of the parameters P _{EMAX, MeNB} and P _{EMAX, SeNB} to the secondary base station and / or the UE.

Up to this point, the initial setting of power distribution between the master base station and the secondary base station has been basically described. The initial values of the parameters P _{EMAX, SeNB} and P _{EMAX, MeNB} are determined by the master base station (responsible for power distribution control) and then transmitted to the secondary base station and the UE. Therefore, the secondary base station can apply these initial values for uplink scheduling, and the UE can apply these initial values for uplink transmission. In the following, in order to maintain an efficient power distribution ratio between the uplink transmission from the UE to the master base station and the uplink transmission from the UE to the secondary base station, Further operations to be followed when updating will be described. Also in the following description, the master base station is responsible for updating the power distribution as needed, i.e. determining the updated values of the parameters P _{EMAX, SeNB} and P _{EMAX, MeNB} and (According to one of several alternative methods presented above) and delivering to a secondary base station or UE or both.

  For this purpose, the master base station uses, for example, information on the path loss or information on the traffic load in at least one of the two radio links as in the case of determining the initial power distribution. The master base station may already have some of this information, such as the traffic load on both radio links (for example, if the master base station forwards secondary base station data to the secondary base station), but usually the master Other information not recognized by the base station is provided to the master base station.

  Specifically, the master base station determines information about the path loss of the first radio link between the UE and the master base station from the (extended) power headroom report of the first radio link received from the UE. can do. Information about the path loss (PL) calculates the power headroom value to be provided to the master base station, as can be understood from the power headroom value equation defined in the background art section defined by the current standard. A master base station that is one of the various parameters that the UE uses to do and knows most of the remaining parameters of this equation can derive information about the path loss that is sought by the UE. The master base station uses mobility measurement reports such as RSRP (Reference Signal Received Power) and RSRQ (Reference Signal Received Quality) in addition to the power headroom report for the purpose of determining the path loss information of the first radio link. be able to.

  On the other hand, the master base station is not aware of the path loss of the second radio link between the UE and the secondary base station required by the UE, and this parameter is also important in updating the power distribution ratio. It is. Information about this path loss can be provided to the master base station in several ways.

  Of course, the information about the path loss of the second radio link can be provided directly to the master base station from the UE, for example in a corresponding MAC control element or another suitable message.

Alternatively, the UE can calculate and create a virtual power headroom report (including virtual power headroom values) for the second radio link to the secondary base station. In the definition of Virtual Power Headroom Reporting (V-PHR) by 3GPP (see the background section for details), when the master base station receives a PH _virtual value from the UE, it derives information on path loss from this value. be able to. In contrast, in a normal power headroom report, the power headroom value is the resource allocation that is not recognized by the master base station (ie, the PUSCH resource allocation represented by the number of valid resource blocks in subframe i. Calculated by the UE based on the bandwidth, M _PUSHC (i)). For this reason, the master base station cannot derive path loss information from a normal power headroom report. As outlined in the background section, the virtual power headroom (virtual PH) is calculated according to Non-Patent Document 3 as follows:
PH _{virtual, c} (i) = P _{CMAX, H, c} − {P 0 _—PUSCH (j) + a (j) + PL _c + f (i)}
The parameter f (i) represents a TPC command specific to the UE, which can be set in either cumulative mode or absolute mode. Since the master base station is not aware of the TPC command sent by the secondary base station, in a further alternative embodiment, set f (i) to 0 when calculating the secondary link virtual power headroom value. Can do.

A virtual power headroom report (V-PHR) for the second radio link can be provided to the master base station so that the master base station can derive information regarding path loss from the virtual power headroom report. For example, the normal power headroom reporting method may be modified and improved so that the UE sends a virtual power headroom report (V-PHR) for the second radio link along with the normal power headroom report to the master base station. it can. This can be understood from FIG. 22, which shows the MAC control elements of the PHR _MeNB and the virtual PHR _SeNB .

  In this way, the normal power headroom reporting method is changed so that the UE can report the first radio link power headroom report and the second radio link power headroom as already defined in the 3GPP standard. It is not only necessary to create a report and send the power headroom report of the first radio link to the master base station and the power headroom report of the second radio link to the secondary base station (normal power headroom). For the report, see, for example, FIG. In addition to this, the UE creates a virtual power headroom report for the second radio link and sends it (preferably along with the normal power headroom report for the first radio link) to the master (not the secondary base station). Send to base station.

FIG. 21 illustrates the behavior of one exemplary UE according to this further embodiment. A UE (more specifically, a MAC entity MAC _MeNB that handles MAC functions / protocols in the direction towards the master base station) is a group of cells associated with the master base station (as already defined by 3GPP standard release 10). The power headroom report including the extended power headroom report information and the virtual power headroom information of the group of cells associated with the secondary base station is generated and transmitted to the master base station. According to the exemplary embodiment shown in FIG. 21, a UE (more specifically a MAC _SeNB ) generates extended power headroom information for a group of cells associated with a secondary base station and transmits it to the secondary base station. To do. As already mentioned above, the present invention is not limited to the case where the virtual power headroom information of the other (secondary) radio link is provided to the master base station. The same principle can be applied when the virtual power headroom information of the group of cells associated with the master base station is provided to the secondary base station together with the power headroom information of the group of cells associated with the secondary base station. it can.

  As shown in FIG. 22, the virtual power headroom associated with the secondary base station should basically be a type 1 power headroom (PH). However, it is also possible to include a type 2 virtual power headroom (ie based on a reference PUCCH format). The virtual power headroom (PH) is always appended to the end of the normal power headroom report for the link to the master base station, according to FIG.

  According to another embodiment, the virtual power headroom information is provided along with the secondary base station identifier. This is particularly necessary in deployments where the UE is connected to one master base station and multiple secondary base stations. For the purpose of conveying the identifier, for example, a reserved bit “R” or bit “V” can be used.

  In a further alternative embodiment, the virtual power headroom reporting information is transmitted in a separate power headroom MAC control element, which is identified by a predefined identifier (eg, logical channel ID). The format of this second power headroom report can be similar to the power headroom MAC control element or extended power headroom MAC control element defined in [2].

  Thus, in one specific embodiment, the standard power headroom reporting method can be modified as follows. That is, whenever a power headroom report to the master base station is triggered (eg, by a periodic report or triggered by an event such as a significant change in path loss), the UE Always send the normal power headroom report to the master base station and the virtual power headroom report associated with the secondary base station together to the master base station.

In summary, the master base station receives information necessary to update the power distribution, preferably periodically. Several more master base station, the parameters _{P EMAX, SeNB} and _{P EMAX,} to determine the updated value of the _MeNB, they were presented and described above in connection with the necessary (e.g. 17 to 19 According to one of the alternative methods) to the secondary base station and / or the UE.

  Up to this step, for example, in a scenario where the efficient power distribution ratio changes as the UE moves and the path loss changes, so it is advantageous to update the power distribution ratio. Have explained. However, the power distribution ratio is also updated in other situations, for example when a particular radio link (eg the first radio link or the second radio link) is not used or becomes unavailable in the uplink. More specifically, a radio link can become inactive on the uplink for several reasons. For example, when a UE expects not to receive downlink data (eg, uplink resource allocation) for a certain length of time, it can enter a DRX state to save battery (corresponding to background art on DRX) (See also explanation).

  Another example is when a radio link failure (ie, at least in the uplink) of the radio link occurs (ie, the radio link is not functioning and can no longer be used for uplink transmission) and therefore enters the radio link failure state. . In at least the above two cases, uplink transmission is not performed on one of the two radio links, or uplink transmission is not possible, so the power distribution ratio at that time is not efficient. Because the power allocated for uplink transmission over a radio link that is not used or unavailable is wasted and power for uplink transmission over the other radio link that is used or not available It is because it is more advantageous to use. In the following, further improvements of the present disclosure to achieve this will be described.

  First, the case where the radio link becomes inactive in the uplink will be described. The UE is monitoring uplink transmissions over the two radio links, and therefore when the radio link becomes inactive on the uplink (ie, an uplink transmission is sent from the UE to the master base station or secondary base station). Can be determined when not expected). As already mentioned above, this is the case when the UE enters DRX mode.

  In a more preferred solution, the UE predicts that the radio link is inactive in order to avoid a power distribution ratio reset being triggered by the radio link being inactive for a very short time. The present disclosure can only be determined when the length of time that the radio link is expected to be inactive in the uplink exceeds a certain time threshold (as described below). You can proceed to the next step. The threshold value can be set to a predetermined value, for example, or set by the master base station via RRC.

  In either case, a UE that is monitoring whether two radio links for uplink transmission to a master base station / secondary base station are deactivated is actually one of the two radio links being inactive. If it becomes active, it will recognize it.

  Assuming that the UE has recognized that the first radio link to the master base station will be inactive on the uplink (preferably over a length of time longer than a predetermined time threshold) (ie, Inform the secondary base station that the first radio link will become inactive in the uplink. Similarly, when the UE recognizes that the second radio link to the secondary base station will be inactive on the uplink (preferably over a length of time longer than a predetermined time threshold) ( That is, it informs the master base station that the second radio link will become inactive in the uplink.

  The UE indicates that the radio link to one base station (i.e., master / secondary base station) becomes inactive in the other base station (i.e., secondary base station / i) in at least one of the following ways: Master base station).

  The UE can use this situation as a trigger for the power headroom report, and thus can create a power headroom report with the corresponding predetermined flag set to a predetermined value (eg, “1”). . The receiving base station can recognize from this predetermined value that the radio link is deactivated in the uplink. More specifically, if the first radio link to the master base station becomes inactive, the UE creates a power headroom report for the second radio link to the secondary base station and creates the second power Set a flag in the headroom report (eg, one of the reserved flags “R” in the power headroom report MAC control element of FIG. 23, or one of the V flags). Instead, the UE creates a virtual power headroom report of the second radio link to the secondary base station, and a flag (for example, the power headroom shown in FIG. 20) in the secondary virtual power headroom report. Set one of the R flags in the last two rows of the reporting MAC control element. According to yet another alternative, the UE creates a virtual power headroom report for the second radio link to the secondary base station, and sets the virtual power headroom value of this secondary virtual power headroom report to a specific predetermined Set to a value (eg, a negative value, because normal V-PH is never negative). In any case, the secondary base station receives one of the above-described indication information (ie, a flag or a predetermined V-PH value) from the UE, and from that information, the first radio link is in the uplink. Can lead to inactivity.

  Conversely, if the second radio link to the secondary base station becomes inactive, the UE creates a power headroom report for the first radio link to the master base station and creates the first power headroom created A flag in the report (eg, one of the reserved flags “R” in the power headroom report MAC control element shown in the first five lines of FIG. 22 or one of the V flags) Set. Instead, the UE creates a virtual power headroom report for the second radio link between the UE and the secondary base station (this virtual power headroom report is as described above for the second radio link). Also used to provide information about path loss to the master base station), a flag in this secondary virtual power headroom report (eg, R in the last row of the power headroom report MAC control element shown in FIG. 22) Flag or V flag). According to yet another alternative, the UE creates a virtual power headroom report for the second radio link between the UE and the secondary base station, and the virtual power headroom value of this secondary virtual power headroom report is A specific predetermined value (for example, a negative value) is set. It should be noted that in this case, the master base station cannot derive information regarding the path loss of the second radio link by the secondary virtual power headroom value. In any case, the master base station receives from the UE one of the indication information mentioned above (i.e. a flag or a predetermined V-PH value) and from that information the second radio link is in the uplink Can lead to inactivity.

In summary, the UE somehow knows that the radio link to one base station (ie, the master base station / secondary base station) becomes inactive, the other base station (ie, the secondary base station / master base station). To inform. The secondary / master base station uses the received indication information so that all output power for uplink transmission by the UE is allocated for uplink transmission over the radio link that remains “active”. The power distribution ratio can be updated. That is, when the secondary base station is notified that the first radio link to the master base station becomes inactive in the uplink, the secondary base station has the relationship P _{EMAX, SeNB} = P _CMAX (or P _{CMAX_L} ) _Determines the new value of P _{EMAX, SeNB} and sends it to the UE (eg, in the MAC control element), so the UE applies the new value for uplink transmission to the secondary base station. Similarly, when the master base station is informed that the second radio link to the secondary base station becomes inactive in the uplink, the master base station will say P _{EMAX, MeNB} = P _CMAX (or P _{CMAX_L} ) From the relationship, determine a new value for P _{EMAX, MeNB and send} that value to the UE (eg, in the MAC control element), so that the UE applies the new value for uplink transmission to the master base station.

  However, the situation where the radio link becomes inactive in this manner is usually temporary, so the power distribution ratio must be returned to the previous ratio in the end. To that end, of course, the UE has just explained that the radio link to one base station (ie master / secondary base station) becomes active again to trigger the resetting of the power distribution ratio again. In a manner similar to that, the other base station (ie secondary base station / master base station) can be informed again.

However, according to another refinement of the present disclosure, this step that the UE notifies once again when the radio link becomes active again in the uplink, by using a corresponding timer at the secondary / master base station, To avoid. More specifically, it is assumed that the reset power distribution ratio is valid only for a specific time length set by the power control timer implemented in the secondary base station and the master base station. After the power control timer expires, power distribution before resetting is applied again. Specifically, the power control timer is implemented in the secondary base station and the master base station, and the secondary base station / master base station receives instruction information about the radio link becoming inactive and a new update of the power output. Triggered when the calculated value is calculated and sent to the UE. When the power control timer expires, the secondary base station / master base station returns the power distribution ratio to the ratio applied before resetting, and thus restored power parameters P _{EMAX, SeNB} / P _{EMAX and MeNB} are transmitted again to the UE.

  The value of the power control timer can be preset or more preferably specified by the UE. Specifically, when the UE recognizes that a radio link is inactive on the uplink, the UE can further determine the length of time that the radio link is expected to be inactive on the uplink. The UE then informs the secondary base station or master base station of the length of time expected to be inactive, and the secondary base station and master base station use this information to set their power control timer be able to. According to an advantageous embodiment, the UE may encode the length of time expected to be inactive into the virtual power headroom value of the secondary virtual power headroom report. For example, this virtual power headroom value not only encodes that the first radio link or the second radio link becomes inactive (eg, by using a negative virtual power headroom value), The length of time expected to be inactive is also encoded (eg, by using another specific negative virtual power headroom value).

  Thus, as explained above, when a radio link becomes inactive in the uplink, the UE power is such that the UE can use its entire UE power resource for the other active radio link. Distribution is reset.

  The situation where the radio link fails (ie, the radio link can no longer be used for uplink (or downlink) transmission) is addressed in a similar manner. The UE monitors the radio link for a failure, and therefore recognizes if a radio link failure of one of the two radio links actually occurs. In that case, the UE informs the other base station about the radio link failure. That is, the UE notifies the master base station in the case of a radio link failure of the second radio link to the secondary base station, and informs the secondary base station in the case of a radio link failure of the first radio link to the master base station. Inform.

  For the radio link failure of the first radio link / second radio link, for example, in a manner similar to that performed in the above case where the radio link becomes inactive in the uplink, the UE Can inform the base station. In this regard, how to reuse the various R or V flags in various (virtual) power headroom reports, or (negative) virtual power headroom values, to avoid unnecessary repetition, See description above.

In summary, the UE informs the secondary base station / master base station in some way about the radio link failure of the radio link to the master base station / secondary base station. The secondary base station / master base station uses the received indication information to distribute power so that all output power for uplink transmission by the UE is allocated for uplink transmission over a functioning radio link. The ratio can be updated. Specifically, when the radio link failure of the first radio link is notified to the secondary base station, the secondary base station uses the new value of P _{EMAX, SeNB} from the relationship P _{EMAX, SeNB} = P _CMAX (or P _{CMAX_L} ). And transmit the value to the UE (eg, in the MAC control element), so the UE applies the new value for uplink transmission to the secondary base station. On the contrary, when the radio link failure of the second radio link is notified to the master base station, the master base station _sets the new value of P _{EMAX, MeNB} from the relationship P _{EMAX, MeNB} = P _CMAX (or P _{CMAX_L} ). Determine and send the value to the UE (eg, in the MAC control element), so the UE applies the new value for uplink transmission to the master base station.

  Furthermore, when the secondary base station / master base station receives the instruction information about the radio link failure from the UE, the secondary base station / master base station can start an appropriate procedure for resolving the radio link failure. For example, when the master base station is informed of the radio link failure of the second radio link, the master base station can change the radio bearer via the secondary base station to the radio bearer via the master base station, or the UE Can determine another secondary base station to connect to. Details of these procedures are already known in the prior art and are therefore known to those skilled in the art, and will not be described here.

In contrast, when the secondary base station is informed about the radio link failure of the first radio link, the secondary base station can perform reconfiguration or handover so that it becomes a new master base station. . The details of this procedure are already known in the prior art and are therefore known to those skilled in the art and will not be described here. The power distribution ratio can then be updated again depending on how and how the radio link failure has been resolved. In order to properly configure the UE power distribution, new parameters P _{EMAX, SeNB} or P _{EMAX, MeNB} or both are determined and provided again to the UE or master base station / secondary base station or both.

Hardware and Software Implementation Another embodiment of the present disclosure relates to implementing the various embodiments described above using hardware and software, or hardware only. In this context, the present disclosure provides a UE (mobile terminal), a master eNodeB (base station) and a secondary eNodeB (base station). The UE and the base station perform the method of the present invention.

  Various embodiments of the present disclosure can be implemented or performed using a computing device (processor). The computing device or processor is, for example, a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device. Furthermore, radio transmitters, radio receivers, and other necessary hardware can be provided in the device (UE, master base station, secondary base station). Various embodiments of the present disclosure may also be implemented or embodied by combinations of these devices.

  Moreover, various embodiments of the present disclosure may also be implemented by software modules. These software modules are executed by a processor or directly in hardware. A combination of software modules and hardware implementation is also possible. The software module may be stored in any type of computer readable storage medium, such as RAM, EPROM, EEPROM, flash memory, registers, hard disk, CD-ROM, DVD, and the like.

  Furthermore, it is noted that individual features of different embodiments of the present disclosure can be the subject of another embodiment, either individually or in any combination.

  It will be apparent to those skilled in the art that various changes and / or modifications can be made to the present disclosure shown in the specific embodiments without departing from the concept or scope of the present disclosure as broadly described. Will be understood. Accordingly, the embodiments presented herein are to be considered in all respects only as illustrative and not restrictive.

Claims (10)

An integrated circuit for controlling a mobile station capable of power headroom reporting in a mobile communication system, the mobile station being connectable to a master base station via a first radio link, and a second radio Connectable to at least one secondary base station via a link;
Calculating by the mobile station a first power headroom report of the first radio link between the mobile station and the master base station;
The calculated first power headroom report, together with information that allows the master base station to determine information regarding the path loss of the second radio link between the mobile station and the secondary base station A process of transmitting from the mobile station to the master base station;
A second power headroom report for the second radio link between the mobile station and the secondary base station is calculated by the mobile station, and the calculated second power headroom report is calculated from the mobile station. Processing to transmit to the secondary base station;
To control the
Integrated circuit. The information based on when the master base station determines the information about the path loss is transmitted in the form of a secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station. ,
The secondary of the second radio link between the mobile station and the secondary base station based on a virtual uplink resource allocation preset for the second radio link to the secondary base station A process of calculating a virtual power headroom report by the mobile station;
To further control the
The integrated circuit according to claim 1. A process for determining, by the master base station, an initial distribution of the maximum transmission power available to the mobile station between the master base station and the secondary base station, the uplink to the master base station Processing for determining the maximum output power (PEMAX, MeNB) of the mobile station for transmission and the maximum output power (PEMAX, SeNB) of the mobile station for uplink transmission to the secondary base station;
Signaling transmitted through the interface between the master base station and the secondary base station, the determined maximum output power (PEMAX, SeNB) of the mobile station for uplink transmission to the secondary base station In the message, processing to transmit from the master base station to the secondary base station,
The determined maximum output power (PEMAX, MeNB) of the mobile station for uplink transmission to the master base station and the determined maximum output of the mobile station for uplink transmission to the secondary base station Processing to transmit power (PEMAX, SeNB) from the master base station to the mobile station in a radio resource control (RRC) message or in a media access control (MAC) control element, or
The determined maximum output power (PEMAX, MeNB) of the mobile station for uplink transmission to the master base station in a radio resource control (RRC) message or in a media access control (MAC) control element Transmit from the master base station to the mobile station, and transmit the determined maximum output power (PEMAX, SeNB) of the mobile station for uplink transmission to the secondary base station from the secondary base station to the mobile station Processing,
To further control the
The integrated circuit according to claim 1 or 2. When the mobile station recognizes that the second radio link between the mobile station and the secondary base station becomes inactive in the uplink, the second radio link becomes inactive in the uplink Information about the mobile station to the master base station,
The information regarding the second radio link becoming inactive in the uplink;
A bit flag having a predetermined value in the first power headroom report of the first radio link between the mobile station and the master base station, or
A bit flag having a predetermined value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station, or
A predetermined power headroom value of the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station;
Provided to the master base station in the form of:
The integrated circuit according to claim 1. Determining, by the mobile station, a length of time that the second radio link is expected to be inactive in the uplink;
The process in which the mobile station provides information to the master base station that the second radio link is inactive in the uplink only if the determined time length exceeds a predetermined time length; Control,
The integrated circuit according to claim 4. The information regarding the second radio link becoming inactive in the uplink is a predetermined power of the secondary virtual power headroom report for the second radio link between the mobile station and the secondary base station. Provided to the master base station in the form of a headroom value;
The predetermined power headroom value is a predetermined negative value that encodes time information regarding a time length predicted by the mobile station that the second radio link is inactive in the uplink,
The integrated circuit according to claim 4 or 5. Receiving the updated distribution of the maximum available transmit power of the mobile station between the master base station and the secondary base station in relation to the second radio link becoming inactive in the uplink Is determined by the master base station based on the received information, at least the updated value of the maximum output power of the mobile station for uplink transmission to the master base station (PEMAX, MeNB) )
Processing for transmitting the updated maximum output power (PEMAX, MeNB) of the mobile station for uplink transmission to the master base station to the mobile station by the master base station;
To further control the
The integrated circuit according to claim 4. When the mobile station recognizes that the first radio link between the mobile station and the master base station is inactive in the uplink, the first radio link is inactive in the uplink The mobile station provides information about the secondary base station,
The information regarding the first radio link becoming inactive in the uplink;
A bit flag having a predetermined value in the second power headroom report of the second radio link between the mobile station and the secondary base station, or
A bit flag having a predetermined value in the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station, or
A predetermined power headroom value of the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station;
Provided to the secondary base station in the form of:
The integrated circuit according to claim 1. Determining by the mobile station a length of time that the first radio link is expected to be inactive in the uplink;
Only when the determined time length exceeds a predetermined time length, control the processing in which the mobile station provides the secondary base station with information about the first radio link becoming inactive in the uplink To
The integrated circuit according to claim 8. The information regarding the first radio link becoming inactive in the uplink is a predetermined power of the secondary virtual power headroom report of the second radio link between the mobile station and the secondary base station. Provided to the secondary base station in the form of a headroom value;
The predetermined power headroom value is a predetermined negative value that encodes time information related to a time length predicted by the mobile station that the first radio link is inactive in the uplink;
The integrated circuit according to claim 8 or 9.

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